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WORKS  OF  ELLEN  H.  RICHARDS 

PUBLISHED   BT 

JOHN  WILEY    &  SONS 
43-45  East  Nineteenth  Street,  New  York 


Laboratory  Notes  on   Industrial    Water    Analysis:   A 
Survey  Course  for  Engrineers. 
8vo,  52  pages.     Cloth,  50c  net. 
The  Cost  of  Cleanness. 

12mo,  V  +  1U9   pages.     Cloth.     Sl.OO. 
The  Cost  of  Living:  as  Modified  by  Sanitary  Science. 

Third  Edition,  Revised.     12mo.     164  pages.     Cloth. 
$1.00. 
Air,  Water,  and  Food;  From  a  Sanitary  Standpoint. 

By   Ellen  H.    Richards  and    Alpheus  G.   Woodman, 
Assistant  Professor  of   Food  Analysis,  Massachusetts 
Institute    of    Terhnolopy.       Third  Edition,   Revised 
and  Enlarged.     8vo.     278  pages.     Cloth.     $2.00. 
The  Cost  of  Food  :   A  Study  in  Dietaries. 
12mo.     161  pages.     Cloth.       $1.00. 

The  Dietary  Computer. 

By  Ellen  H.  Richards,  Instructor  in  Sanitary  Chem- 
istry, Massachusetts  Institute  of  Technology,  assisted 
by  Louise  Harding  Williams.     $1.50  net.     Pamphlet 
separately,  $1.00  net. 
The  Cost  of  Shelter. 

12mo.     vi  + 136  pages.     Illustrated.     Cloth.     $1.00. 

"Cost  of  Living:"  Series. 

1.  Cost  of  Living.  2.  Cost  of  Food.  3.  Cost  of 
Shelter.  4.  Cost  of  Cleanness.  12mo.  Cloth.  4 
vols,  in  a  box.     $4.00. 


Published  by  WHITCOMB   &   BARROWS 
Huntington  Chambers 

The  Chemistry  of  Cooking:  and  Cleaning:. 

By    Ellen    H.  Richards  and  S.  Maria  Elliott.      158 
pages.     Cloth.     $1.00. 
Food  Materials  and  their  Adulterations. 

183  pages.     Cloth.     $1.00. 

Home  Sanitation. 

Revised  Edition.     Edited  by  Ellen  H.  Richards  and 
Marion  Talbot.     85  pages.     Paper.     25c. 

Plain  Words  about  Food. 

The    Ruraford    Leaflets.      Illustrated.       176  pages. 

Cloth.     $1.00. 
First  Lessons  on  Food  Diet. 

52  pages.     Cloth.     30c  net. 
The  Art  of  Right=Living:. 

50  pages.     Cloth.         50c  net. 

Sanitation  in  Dally   Life. 

82  pages.      Cloth.      6oc.  net. 


AIR,  WATER,  AND  FOOD 


FROM   A   SANITARY   STANDPOINT. 


BY 


ELLEN  H.  RICHARDS  and  ALPHEUS  G.  WOODMAN. 


Instructor  in  Sanitary  Chemistry. 
Massachusttts  Institute  of  Technology, 


Assistant  Projessor  of  Food  Analysis, 
Massachusetts    Institute    of    Technology. 


"These  cannot  be  taken  as  sufficient  ...  in  these  times  when 
every  word  spoken  finds  at  once  a  ready  doubter,  if  not  an  opponent. 
They  are.  however,  specimens,  and  will  serve  to  make  comparisons 
in  time  to  come."— Angus  Smith. 

"The  ideal  scientific  mind,  therefore,  must  always  be  held  in  a 
state  of  balance  which  the  slightest  new  evidence  may  chang^e  in  one 
direction  or  another.  It  is  in  a  constant  state  of  skepticism,  knowiog 
full  well  that  nothing  is  certain."— Henry  A.  Rowland. 


THIRD    EDITION,   REVISED    AND    ENLARGED. 

FIRST    THOUSAND. 


OF    THE 

UNIVERSITY 

OF 

NEW   YORK: 
JOHN    WTLEY    &    SONS. 

London:    CHAPMAN  Sz  HALL.  Limited. 

1909. 


Copyright.  1900.  1904.  1909, 

BY 

ELLEN   H.  RICHARDS  and  ALPHEUS  G.  WOODMAN. 


tBift  (^cfmtific  frraa 

Snbrrt  Brummiinit  an&  Gloraiiang 

^em  fork 


/iof 

HEALTH 

PREFACE   TO  THE  THIRD  EDITION.     ^^ 


The  great  increase  of  attention  to  the  relations  of 
physical  environment  to  mental  and  moral  welfare  leads 
the  authors  to  hope  that  this  revised  and  enlarged  edition 
will  meet  with  approval  by  the  body  of  seekers  after  truth 
along  these  lines  of  study  and  investigation. 

More  clearly  than  any  one  else  they  recognize  the  omis- 
sions and  shortcomings  of  any  book  dealing  with  so  compre  • 
hensive  a  subject  under  the  limitations  of  a  short  school 
course.  Therefore  a  suggestive  rather  than  a  complete 
treatment  has  been  adopted,  and  a  certain  conservatism 
has  governed  the  discussion  of  some  subjects  which  to 
treat  fully  would  require  too  much  space  as  well  as  a 
previous  training  impossible  to  assume. 

The  chapters  on  analytical  methods  have  been  con- 
siderably enlarged;  the  character  of  the  matter  added 
tends  to  make  the  work  more  adapted  to  the  needs  of 
the  chemical  and  sanitary  engineer  as  well  as  to  the  general 
student  and  householder.  In  a  subject  so  rapidly  advanc- 
ing the  printed  page  can  hardly  hope  to  keep  fully  abreast 
of  the  times,  but  all  the  methods  have  been  reviewed  or 
modified,  and  tentative  ones  have  been  retained  or  dropped 
as  experience  has  indicated  their  value. 

The  bibliography  has  been  revised  and  brought  up  to 
date. 


CONTENTS. 


tHAPTiiR  PAGE 

I.  Three  Essentials  of  Human  Existence i 

II.  Air:  Composition,  Impurities,  Relation  to  Human  Life lo 

IIL  The  Problem  of  Ventilation 19 

IV.  Methods  of  Examination 27 

V.  Water:  Source,  Properties,  Solvent  Power,  as  a  Carrier.  57 
VI.  The  Problem  of  Safe  Water  and  Interpretation  of  Analy- 
ses    76 

VII.  Methods  of  Examination 96 

VIII.  Food   in    Relation    to    Human    Life,    Definition,    Sources, 

Classes,  Dietaries 142 

IX.  Adulteration  and  Sophistication  of  Food  Materials i57 

X.  Methods  of  Food  Analysis 167 

Appendices,  Tables,  Reagents 235 

Bibliography 263 


..         OP  THE 

UNIVERSITY 

OF 


AIR,  WATER,  AND  FOOD, 


CHAPTER  I. 

THREE   ESSENTIALS   OF   HUMAN   EXISTENCE. 

Air,  water,  and  food  are  three  essentials  for  healthful 
human  life.  Sanitary  Chemistry  deals  with  these  three  com- 
modities in  their  relation  to  the  needs  of  daily  existence: 
first,  as  to  their  normal  composition;  second,  as  to  natural 
variations  from  the  normal;  third,  as  to  artificial  variations — 
those  produced  directly  by  human  agency  with  benevolent 
intention,  or  resulting  from  carelessness  or  cupidity.  A 
large  portion  of  the  problems  of  public  health  come  under 
these  heads,  and  a  discussion  of  them  in  the  broadest  sense 
includes  a  consideration  of  engineering  questions  and  of 
municipal  finances.  This,  however,  is  beyond  the  scope  of 
the  present  work. 

The  following  pages  will  deal  chiefly  with  such  portions 
of  the  subject  of  Sanitarv^  Chemistry  as  come  directly  under 
individual  control,  or  which  require  the  education  of  indi- 
viduals in  order  to  make  up  the  mass  of  public  opinion 
which  shall  support  the  city  or  state  in  carrying  out  sanitary 
measures. 

A  notable  interest  in  the  subject  of  individual  health  as 


■2  AIR,    WATER,    AND    FOOD. 

a  means  of  securing  the  highest  individual  capacity  both  for 
work  and  for  pleasure  is  being  aroused  as  the  application  of 
the  principles  governing  the  evolutionary  progress  of  other 
iorms  of  living  matter  is  seen  to  extend  to  mankind. 

Will  power  may  guide  human  forces  in  most  economi- 
cal ways,  and  may  concentrate  energy  upon  a  focal  point  so 
as  to  seem  to  accomplish  superhuman  feats,  but  it  cannot 
create  force  out  of  nothing.  There  is  a  law  of  conservation 
of  human  energy.  The  human  body,  in  order  to  carry  on 
all  its  functions  to  the  best  advantage,  especially  those  of  the 
highest  thought  for  the  longest  time,  must  be  placed  under 
the  best  conditions  and  must  be  supplied  with  dean  air,  safe 
water,  and  good  food,  and  must  be  able  to  appropriate  them 
to  its  use.  The  day  is  not  far  distant  when  a  city  w^ill  be 
held  as  responsible  for  the  purity  of  the  air  in  its  school- 
houses,  the  cleanliness  of  the  water  in  its  reservoirs,  and  the 
reliability  of  the  food  sold  in  its  markets  as  it  now  is  for  the 
condition  of  its  streets  and  bridges.  Nor  will  the  years  be 
many  before  educational  institutions  will  be  held  as  respon- 
sible for  the  condition  of  the  bodies  as  of  the  minds  of  the 
pupils  committed  to  their  care:  when  a  chair  of  Sanitary 
Science  will  be  considered  as  important  as  a  chair  of  Greek 
or  Mathematics;  when  the  comoetency  of  the  food-purveyor 
Avill  have  as  much  weight  with  intelligent  patrons  as  the 
scholarly  reputation  of  any  member  of  the  Faculty.  Within 
a  still  shorter  time  will  catalogues  call  the  attention  of  the 
interested  public  to  the  ventilation  of  college  halls  and  dor- 
mitories, as  w^ell  as  to  the  exterior  appearance  and  location. 

These  results  can  be  brought  about  only  when  the  stu- 
dents themselves  appreciate  the  possibilities  of  increased 
mental  production  under  conditions  of  decreased  friction, 
such  as  can  be  found  only  when  the  requirements  of  health 
are  perfectlv  fulfilled. 


THREE    ESSENTIALS    OF    HUMAN    EXISTENCE.  3 

Of  the  three  essentials,  air  may  well  be  considered  first, 
although  its  office  is  to  convert  food  already  taken  into  heat 
and  energy.  Its  exclusion  only  for  a  few  minutes  causes 
death,  and  in  quantity  used  it  far  exceeds  the  other  two. 
Again,  so  important  is  the  action  of  air  that  the  quality  of 
food  is  of  far  less  consequence  when  abundant  oxygen  is 
present,  as  in  pure  air,  than  when  it  is  present  in  lessened 
quantity,  as  in  air  vitiated  by  foreign  substances. 

Individual  habit  has  much  to  do  with  the  appreciation 
of  good  air,  and  as  our  knowledge  of  the  value  of  an  abun- 
dance of  this  substance  in  securing  great  efficiency  in  the 
human  being  increases,  we  shall  be  led  to  attach  more  im- 
portance to  the  sufficiency  of  the  supply. 

In  northern  climates  air  is  not  free  to  all  in  the  sense  of 
costing  nothing,  for  the  coming  of  fresh  air  into  the  house 
means  an  accompaniment  of  cold  which  must  be  counter- 
acted by  the  consumption  of  fuel.  A  mistaken  idea  of  econ- 
omy leads  householders,  school  boards,  and  college  trustees 
to  limit  the  size  of  the  air-ducts  as  well  as  of  the  rooms.  It 
is  therefore  necessary  to  emphasize  the  facts  which  science 
has  fully  esta'blished.  in  order  to  secure  the  survival  of  the 
fittest  of  the  race  under  the  present  pressure  of  economic 
conditions,  which  take  so  little  account  of  the  highest  wel- 
fare of  the  human  machine. 

Air,  water,  and  soil  are  the  common  possessions  of  man- 
kind. It  is  impossible  for  man  to  use  either  selfishly  without 
injur}^  to  his  neighbor  and  without  squandering  his  inheri- 
tance. Primitive  man  could  leave  a  given  spot  when  the 
soil  became  offensive,  and  neighbors  were  then  too  few  to 
require  consideration;  but  neither  man  nor  beast  could  with 
impunity  foul  the  stream  for  his  neighbor  who  had  rights 
below  him.  The  soil  is  permanent:  one  knows  where  to  look 
for  it  and  its  pollution.     Air  is  abundant  and  is  kept  in  con- 


4  AIR,    WATER,    AND    FOOD. 

stant  motion  by  forces  of  nature  beyond  human  control,  so 
that,  save  in  the  neighborhood  of  an  exceptionally  offensive 
factory,  man  does  not  often  foul  the  free  air  of  heaven;  it  is 
only  when  he  confines  it  within  unwonted  bounds  that  it 
becomes  a  menace. 

Water  is  the  next  precious  commodity  of  the  three. 
Without  it  man  dies  in  a  few  days;  without  it  the  soil  is  bar- 
ren; without  it  air  in  motion  parches  all  vegetation  and 
carries  clouds  of  dust-particles;  without  it  there  is  no  life. 
As  population  increases  it  becomes  necessary  to  collect  as 
much  of  the  rainfall  as  possible,  to  store  it  until  needed,  and 
to  use  it  with  discretion.  After  use  it  is  often  loaded  with 
impurities  and  sent  to  deal  death  and  destruction  to  those 
who  require  it  later,  and  yet,  in  nature's  plan,  it  is  the  carrier 
of  the  world,  and  rightly  treated  and  carefully  husbanded 
there  is  enough  for  the  needs  of  all.  Its  presence  or  absence 
has  been  the  controlling  force  in  determining  the  habitations 
of  men.  In  its  office  of  carrier  it  not  only  brings  nourishment 
in  solution  to  the  tissues  of  the  human  body,  but  also  carries 
away  the  refuse  material.  It  is  a  cardinal  principle  in  all 
sanitary  reforms  to  get  rid  of  that  which  is  useless  as  soon  as 
possible.  Too  little  water  allows  accumulation  of  waste 
material  and  a  clogging  of  the  bodily  drainage  system. 

The  average  quantity  needed  daily  by  the  human  body  is 
about  three  quarts.  Of  this  a  greater  or  less  proportion  is 
taken  in  food,  so  that  at  times  only  from  a  pint  to  a  quart 
need  be  taken  in  the  form  of  water  as  such. 

Next  in  importance  to  quantity  is  the  quality,  dependent 
somewhat  upon  the  uses  to  which  it  is  to  be  put.  As  a  rule, 
the  moderately  soft  waters  are  the  best  for  any  purpose. 
For  drinking  purposes  water  must  be  free  from  dangers  to 
health  in  the  way  of  poisonous  metals,  decomposing  matters, 
and    disease-germs.     For    domestic    use    economy    requires. 


THREE    ESSENTIALS    OE    HUMAN'    EXISTENCE.  5 

that  it  should  not  decompose  too  much  soap.  Manufactur- 
ing interests  require  that  it  should  not  give  too  much  scale 
to  boilers;  for  agriculture  there  should  not  be  too  much 
alkali. 

From  the  nature  of  things,  no  one  family  or  city  can  have 
sole  control  of  a  given  body  of  water.  Those  on  the  high- 
lands may  have  the  first  use  of  the  water,  which  then  perco- 
lates to  a  lower  level  and  is  used  by  the  people  on  the  slopes 
over  and  over  before  it  reaches  the  sea  to  start  again  on 
its  cycle  of  vapor,  cloud  and  rain,  brook  and  river.  Al- 
though receiving  impurities  each  time,  there  are  many 
beneficent  influences  at  work  to  overcome  the  evils  resulting 
from  this  repeated  use.  That  which  is  dissolved  from  one 
portion  of  earth  may  be  deposited  on  another.  As  the  plant 
is  the  scavenger  of  the  air,  withdrawing  the  carbon  dioxide 
with  which  it  would  otherwise  become  loaded,  so  the  water 
has  also  its  plant  life,  purifying  it  and  withdrawing  that  which 
would  otherwise  soon  render  it  unfit  for  any  use. 

Pure  water  is  found  only  in  the  chemical  laboratory;  the 
most  that  can  be  hoped  for  is  that  human  beings  may  secure 
for  themselves  water  w^hich  is  safe  to  drink,  which  will  not 
impair  the  ef^ciency  of  the  human  machine. 

The  importance  of  the  third  essential  for  human  life, 
food,  and  the  close  interdependence  of  all  three,  may  be 
clearly  shown.  Of  little  use  is  it  to  provide  pure  air  and 
clean  water  if  the  substances  eaten  are  not*  capable  of  com- 
bining w^ith  the  oxygen  of  the  air  or  of  being  dissolved  in 
the  water  or  the  digestive  juices;  of  less  use  still  is  it  to  par- 
take of  substances  which  act  as  irritants  and  poisons  on  the 
tissues  which  they  should  nourish,  and  thus  prevent  healthful 
metabolism  and  respiratory  exchange. 

And  yet  a  large  majority  of  those  who  have  acquired 
some  notion  of  the  meaning  and  importance  of  pure  air  and 


6  AIR,    WATER,    AND    FOOD. 

are  beginning  to  consider  it  worth  while  to  strive  for  clean 
water  pay  not  the  least  attention  to  the  sanitary  qualities  of 
food;  the  palatable  and  aesthetic  aspects  only  appeal  to 
them. 

Steam-power  is  produced  by  the  combustion  of  coal  or 
oil.  Human  force  is  derived  by  releasing  the  stored  energy 
of  the  food  in  the  body.  The  delicately  balanced  mechan"sm 
of  the  human  body  suffers  even  more  from  friction  than  the 
most  sensitive  machine,  and  the  greatest  loss  of  potential 
human  energy  occurs  through  ignorance,  carelessness,  and 
reckless  disregard  of  nature's  laws  in  regard  to  food. 

It  is  necessary  to  know,  first,  what  is  the  normal  compo- 
sition of  a  given  food-material.  This  is  found  by  analyses 
of  many  typical  samples.  Second,  is  the  sample  under  con- 
sideration normal?  To  answer  this  requires  an  analysis  of  it, 
and  a  comparison  of  the  results  with  standards.  If  it  is  not 
normal,  in  what  way  does  it  depart  from  the  standard  both 
in  healthfulness  and  in  quality?  Third,  if  a  food-substance 
is  normal,  what  are  its  valuable  ingredients  and  in  what  pro- 
portions are  they  to  be  used  in  the  daily  diet? 

In  regard  to  meat,  milk,  and  fish,  the  sanitary  aspect  for 
the  chemist  resolves  itself  into  two  questions:  Is  the  sub- 
stance so  changed  as  to  become  a  possible  source  of  poison- 
ous products?  Or  has  anything  in  the  nature  of  a  preserva- 
tive been  added  to  it?  If  so,  is  it  of  a  nature  injurious  to 
man? 

There  is,  however,  a  great  range  of  quality  in  some  of  the 
most  abundant  foodstuffs,  such  as  the  cereals,  especially  in 
the  nitrogen  content.  This  is  most  important  to  the  vege- 
tarian and  to  institutions  where  economy  must  be  practised. 
The  following  variations  in  the  composition  of  leading  cereals 
will  illustrate: 


Fibre. 

Ash. 

20. oS 

8.64 

4-45 

1.34 

1.30 

2.03 

7-71 

3-93 

0.99 

0.S2 

THREE    ESSENTIALS    OF    III'MAX    EXISTENCE 

Water      Nitrogenous     Crude  Carbo- 

Substance.         rat.  hydrates. 

Oats,  maximum 20.80  18.84  10.65  64.63 

"      minimum 6.21  6.00  2. 11  48.69 

*'      American  hulled.  12. 11  13-57  7-68  63.37 

Corn,  maximum 22.20  14.31  8.87  52.08 

minimum 4. 68  5.55  1.73  72.75 

One  sample  of  wheat  flour  may  contain  14  per  cent,  of  nitro- 
genous substance,  another  may  yield  only  9.  A  day's  ration, 
500  grams,  will  give  70  grams  of  gluten,  etc.,  in  the  one 
case  and  only  45  in  the  other.  This  difference  of  25  grams 
would  be  a  serious  factor  in  the  dietary  of  an  institution 
where  little  additional  proteid  is  given,  and  it  alone  might 
be  the  cause  of  dangerous  under-nutrition. 

The  next  step  would  naturally  be  to  determine  how 
definitely  these  varying  percentages  mean  varyine  nutrition. 
To  this  end  a  study  of  vegetable  nitrogenous  oroducts  in 
their  combination  or  contact  with  cellulose,  starch,  and  min- 
eral matter  is  needed.  Much  work  remains  to  De  done 
before  these  questions  can  be  even  approximatelv  answered. 

At  the  low  cost  of  one  cent  a  pound,  common  vegetables 
yield  only  about  one-fifth  as  much  nutriment  as  one  cent's 
worth  of  flour,  yet  they  contain  essential  elements  and  de- 
serve to  be  carefully  studied. 

Dried  fruits  and  nuts  are  much  undervalued  as  articles  of 
food,  as  are  rice  and  lentils.     (See  table,  page  150.) 

The  discussion  of  food  values  will  be  found  in  Chapter 
VIIl. 

Probably  the  widest  field  for  the  sanitary  chemist  to-day 
is  the  study  of  the  so-called  predigested  foods,  infant  foods, 
"  hygienic  "  preparations,  two-minute  cereals,  and  the  count- 
less proprietary  packages,  which,  designed  to  meet  the  de- 
mand for  quick  results,  prove  traps  for  the  unwary. 

Therefore  the  sanitary  aspect  of  food  demands  a  study 


;8  AIR,    WATER,    AND    FOOD. 

of  normal  food  and  food  value  even  more  tl  m  of  adulterants 
or  of  poisonous  food,  ptomaines  and  toxines.  The  cultiva- 
tion of  intelligent  public  opinion  is  most  important,  and  each 
student  should  go  out  from  a  sanitary  laboratory  a  mission- 
ary to  his  fellow  men.  That  is,  the  ofifice  of  a  laboratory 
of  sanitary  chemistry  should  be  so  to  diffuse  knowledge  as 
to  make  it  impossible  for  educated  people  to  be  deluded  by 
the  representations  of  unprincipled  dealers.  Freedom  from 
superstition  is  just  as  important  in  this  as  in  the  domain  of 
astronomy  or  physics.  So  long  as  chemists  are  employed 
by  manufacturing  concerns  in  making  adulterated  and 
fraudulent  foodstuffs,  so  long  must  other  chemists  be  em- 
ployed in  protecting  the  people  until  the  public  in  general 
becomes  wiser.  A  part  of  the  common  knowledge  of  the 
race  should  be  the  essentials  of  healthful  living,  in  order  that 
tlie  full  measure  of  human  progress  may  be  enjoyed. 

There  is  needed  a  greater  respect  for  food  and  its  func- 
tions in  the  human  body,  a  better  knowledge  of  its  effect  on 
the  daily  output  of  energy,  its  absolute  relations  to  health 
and  life,  and  the  enjoyment  of  the  same.  The  familiarity 
with  these  facts  which  is  given  by  a  few  hours'  work  in  the 
laboratory  will  make  a  lasting  impression  and  will  enable  the 
student  to  benefit  his  whole  life,  even  if  he  never  uses  it  pro- 
fessionally. It  is  purely  scientific  knowledge,  just  as  much 
as  that  derived  from  a  study  of  the  phases  of  the  moon  or  the 
formulas  of  integration. 

The  variety  of  operations  in  such  work,  calling  for  great 
diversity  of  apparatus  and  methods,  is  an  educational  factor 
not  to  be  overlooked  in  laboratory  training. 

For  all  detailed  discussions  and  methods  the  reader  .s 
referred  to  such  works  as  those  of  Wiley,  Allen,  Leach,  etc., 
but  for  the  student  who  needs  to  study,  as  a  part  of  general 
.{education,  only  typical  substances,  and  such  methods  as  can 


THREE    ESSENTIALS  OF   HUMAN   EXISTENCE.  9 

be  carried  out  within  the  limits  of  laboratory  exercises  in 
a  college  curriculum,  the  following  pages  are  written.  Not 
enough  is  given  to  frighten  or  discourage  the  student,  but 
enough,  it  is  hoped,  to  arouse  an  interest  which  will  impel 
him  at  every  subsequent  opportunity  to  seek  for  more  and 
wider  knowledge. 

Food  is  too  generally  regarded  as  a  private,  individual 
matter  rather  than  as  a  branch  of  social  economy;  it  is, 
however,  too  fundamental  to  the  welfare  of  the  race  to  be 
neglected.  Society,  in  order  to  protect  itself,  must  take 
cognizance  of  the  questions  relative  to  food  and  nutrition. 

Formerly  each  race  adapted  itself  to  its  environment  and 
trained  its  digestion  in  accordance  with  the  available  food 
supply.  In  America  to-day  the  question  is  not  how  to  get 
food  enough,  but  how  to  choose  from  the  bewildering  variety 
offered  that  which  shall  best  promote  the  health  and  develop 
the  powers  of  the  human  being,  and,  what  is  of  equal  im- 
portance, how  to  avoid  over-indulgence,  which  weakens  the 
moral  fibre  and  lessens  mental  and  physical  efficiency.  In 
spite  of  all  preaching,  few  really  believe  that  plain  living 
goes  with  high  thinking.  Professor  Patten  says  that  the 
ideal  of  health  is  to  obtain  complete  nutrition.  Over-nutri- 
tion as  well  as  under-nutrition  weakens  the  body  and  sub- 
jects it  to  evils  that  make  it  incapable  of  survival. 

No  other  form  of  social  service  will  give  so  full  a  return 
for  effort  expended  as  the  help  given  toward  better  diet 
for  children  and  students.  Fortunately  help  is  coming  fast. 
The  United  States  Government  is  giving  much  study  to 
food  problems,  and  by  publications  is  making  available  the 
work  of  other  countries.  The  later  bulletins  listed  in  the 
bibliography  at  the  end  of  this  volume  are  especially  valu- 
able. What  is  now  needed  is  a  general  recognition  of  the 
importance  of  the  subject. 


CHAPTER  II. 
air:     composition;     impurities;     relation    to    human 

LIFE. 

The  average  adult  human  being  makes  about  eighteen 
involuntary  respirations  per  minute.  The  tidal  volume  of 
air  is  from  300  to  500  cubic  centimeters  (30  cu.  in.),  about 
2800  cubic  centimeters  (170  cu.  in.)  remaining  in  the  lungs 
unless  voluntarily  expelled  by  deep  breathing.  The  total 
volume  expelled  is  often  called  the  vital  capacity,  and  is  about 
3400  cubic  centimeters  for  men  and  2500  for  women.  Even 
when  at  rest  a  volume  of  7000  to  12,000  liters  (250  to  420 
cu.  ft.)  of  air  passes  through  the  lungs  of  each  individual  in 
twenty-four  hours.  Under  conditions  of  exercise  more  or 
less  prolonged  or  violent  this  volume  may  be  doubled.  The 
composition  of  the  normal  inspired  air  by  volume  is  approxi- 
rnately:  nitrogen  and  argon  79  per  cent.,  oxygen  20.9  per 
cent.,  other  constituents  o.i  per  cent.  The  air  as  it  leaves 
the  lungs  contains  nitrogen  79.5  per  cent.,  oxygen  16.0  per 
cent.,  carbon  dioxide  4.4  per  cent.,  and  is  saturated  with 
water- vapor.  There  has  therefore  taken  place  an  inter- 
change of  gases  (called  the  respiratory  exchange),  by  which 
oxygen  has  passed  into  the  fluids  of  the  body,  and  carbon 
dioxide  into  the  air  contained  within  the  lung-cells.  Only 
about  one-fifth  of  the  total  oxygen  is  abstracted  during  each 
tide. 

If  the  composition  of  the  inspired  air  varies  from  the 


air:    relation  ro  human  life.  ii 

normal,  this  exchange  is  disturbed,  owing  to  the  difference 
in  gaseous  pressure  and  in  rate  of  absorption  which  this 
variation  causes.  So  deHcate  is  the  balance  of  the  active 
forces  that  serious  disturbance  of  the  functions  of  the  living 
organism  occurs  if  the  percentage  of  oxygen  is  lessened  by 
one  or  two  tenths,  or  if  the  pressure  is  raised  or  lowered  by 
a  fraction  of  an  atmosphere.  It  is  true  that,  like  a  tree 
bending  before  the  wind,  the  organism  soon  adapts  itself  to 
changed  circumstances,  provided  the  change  is  not  too  great 
nor  too  suddenly  made;  but,  like  the  exposed  tree,  the  living 
being  is  never  quite  so  vigorous  and  symmetrical  as  it  would 
have  been  without  the  effort  to  overcome  disadvantageous 
conditions. 

That  a  permanent  or  habitual  lowering  of  the  oxygen  in 
inspired  air  must  be  harmful  will  be  readily  seen  from  a  con- 
sideration of  the  office  of  this  gas  in  the  body.  To  Lavoisier 
and  Laplace  we  owe  the  knowledge  that  animal  heat  is  de- 
rived from  a  process  of  combustion.  Lavoisier  held,  how- 
ever, that  the  seat  of  this  combustion  was  in  the  lungs,  and 
it  is  to  Pfliiger  and  his  pupils  that  we  are  indebted  for  the 
proofs  that  it  is  in  the  tissues  themselves,  while  the  lungs 
serve  as  a  clearing-house  or  centre  of  exchange. 

By  the  union  of  the  oxygen  with  the  substances  found  in 
the  tissues  and  brought  to  them  by  the  circulating  fluids  of 
the  body  from  the  digested  food,  the  heat  necessary  for  the 
life  and  work  of  the  body  is  produced.  This  heat  is  needed 
to  keep  the  tissues  at  the  temperature  at  which  they  can  best 
accomplish  their  work,  to  give  mechanical  power  for  the  in- 
voluntary action  of  heart  and  lungs,  for  the  processes  of 
assimilation,  and  to  furnish  the  energy  for  all  voluntary  work 
and  thought.  Thus  both  water  and  food  are  intimately  con- 
cerned in  the  processes  in  which  air  is  an  essential  factor. 
The  statement  made  in  the  first  sentence  of  Chapter  I  is 


12  ■  AIR,    WATER,    AND    FOOD. 

•therefore  justified,  namely,  that  air,  water,  and  food  together 
are  three  essentials  of  human  existence.  A  certain  relation 
between  the  three  means  health,  and  any  disturbance  of  this 
relation  means  unhealth,  by  which  term  may  be  designated 
a  condition  of  less  than  perfect  health  not  yet  so  serious  as 
to  be  called  sickness. 

Air  being  a  mere  mixture  of  the  gases  nitrogen  and  oxy- 
gen, in  no  definite  atomic  proportions,  and  carrying  varying 
amounts  of  other  substances,  gaseous  and  suspended  parti- 
cles, no  definite  composition  can  be  given.  The  difference 
between  the  air  over  sea  or  forest  plateau  and  that  of  city 
streets  or  of  crowded  tenements  seems  only  slight  if  expressed 
in  per  cent.  From  20.98  per  cent,  of  oxygen  in  the  first  to 
20.87  and  20.60  in  the  last;  from  .022  per  cent,  of  carbon 
dioxide  in  the  purest  air  to  .045  in  cities  and  .33  in  rooms,  are 
the  common  variations;  and  yet  the  effect  of  these  apparently 
small  differences  on  human  beings  subjected  to  them  is  very 
noticeable.  It  is  customary  to  enhance  these  differences  by 
expressing  the  results  in  parts  per  10,000. 

That  the  carbon  dioxide  is  of  itself  a  disturbing  factor  is 
indicated  by  the  observed  fact  that  air  which  has  had  the  per 
cent,  of  oxygen  reduced  by  combustion  to  a  point  at  which 
a  candle  will  no  longer  burn  may  be  made  again  a  supporter 
of  combustion  by  the  removal  of  the  cafbon  dioxide. 

A  practical  application  of  this  principle  is  made  in  the 
devices  used  in  diving  and  in  entering  mines  filled  with  irre- 
spirable  gases. 

There  is  a  sensible  effort  in  breathing,  and  a  feeling  of 
discomfort  is  usually  experienced,  if  the  carbon  dioxide  ac- 
cumulates to  ten  times  the  normal  amount,  or  40  parts  per 
10,000  instead  of  4.  This  is  probably  due  to  its  solubility 
and  to  its  interference  with  the  respiratory  exchange,  since 
the  interchange  of  gases  is  influenced  by  their  "  partial  pres- 


air:    relation  to  human  life.  13 

sures."     Each  gas   forming  part   of  a  mechanical   mixture 

exerts  a  partial  pressure  proportional  to  its  percentage  of  the 

mixture.     For  example,  if  atmospheric  air,  containing  20.81 

per  cent,  of  oxygen,  is  at  760  millimeters  barometric  pres- 

20.81 
sure,  the  partial  pressure  of  the  oxygen  would  be X 

760=158.15  millimeters.  The  following  partial  pressures 
of  oxygen  and  carbon  dioxide  in  inspired  air  and  in  the  lung- 
cells  show  the  extent  of  variation  in  different  parts  of  the 
respiratory  tract: 

Inspired  Air.  Lung-cells. 

Oxygen    158.15  mm.  122  mm. 

Carbon  dioxide....        0.30  mm.  38  mm. 

Gas  will  always  tend  to  diffuse  from  the  region  of  high- 
est to  that  of  lowest  pressure.  Hence  the  reason  for  the 
great  influence  of  pressure  in  causing  the  diffusion  of  oxygen 
from  the  inspired  air  into  the  lung-cells  and  for  the  converse 
movement  of  carbon  dioxide.  That  variation  in  pressure 
has  much  to  do  with  the  discomfort  is  shown  in  the  so-called 
mountain-sickness,  experienced  at  high  altitudes  in  rarefied 
air,  and  in  the  so-called  caisson-disease,  developed  in  men 
working  in  compressed  air.  If  the  passage  from  the  caissons 
to  the  open  air  is  made  gradually,  there  is  little  trouble,  but 
a  quick  change  is  often  dangerous.  A  sort  of  mountain- 
sickness  is  experienced  by  many  on  entering  a  close  room 
from  the  outside  air.  Usually  this  passes  away  in  a  measure 
as  the  organism  accommodates  itself  to  the  new  conditions. 
Even  if  the  symptoms  are  not  severe,  there  is  a  dulness  or 
an  irritability  which  is  not  conducive  to  the  best  apprehen- 
sion of  a  difificult  subject  or  to  the  fullest  enjoyment  of  an 
entertainment. 

This  lessening  of  mental  capacity  is  especially  to  be  de- 


14  AIR,    WATER,    AND    FOOD. 

plored  in  the  case  of  school-children,  who  are  at  an  age  when 
respiration  is  most  frequent  and  the  need  of  pure  air  the 
greatest,  and  also  when  economy  of  efifort  is  most  demanded. 

It  has  been  said  that  from  the  study  of  the  physiological 
effects  of  close  air  it  seems  to  be  indicated  that  the  evil  is 
due  to  the  change  in  the  respiratory  quotient  and  to  the  con- 
sequent change  in  blood-pressure,  which  interferes  with  the 
circulation.  The  respiratory  quotient  is  obtained  by  divid- 
ing the  volume  of  carbon  dioxide  given  off  by  that  of  the 
oxygen  absorbed,  and  indicates  how  much  of  the  oxygen  has 
combined  with  carbon  to  form  carbon  dioxide,  since  one  vol- 
ume of  oxygen  combines  with  cafbon  to  form  one  volume  of 
carbon  dioxide.  The  rate  of  exchange  is  influenced  by 
questions  of  pressure,  exposure,  temperature,  and  water- 
vapor  or  moisture,  muscular  activity,  and  the  like. 

Water-vapor  is  the  most  variable  constituent,  due  to  the 
changing  capacity  of  air  for  moisture  at  different  tempera- 
tures and  to  the  character  of  the  earth's  surface.  Whether 
over  land  or  water,  cultivated  or  forest  region,  air  at  o°  C. 
contains  only  4.87  grams  of  water  per  cubic  meter,  while  air  at 
60°  F.  (15°  C.)  can  take  up  12.76  grams,  and  at  90°  F.  holds 
33.92  grams.  Since  the  human  body  is  constmtV  giving  off 
moisture  from  skin  and  lungs,  and  since  this  exhalation  is  an 
important  factor  in  the  bodily  economy,  the  presence  of  ex- 
cessive moisture  in  the  air  exercises  a  decided  effect. 

On  clear,  invigorating  days  the  moisture  in  the  air  may 
be  only  30  or  50  per  cent,  of  that  required  for  complete  satu- 
ration at  the  given  temperature,  and  althou2:h  the  ther- 
mometer reading  may  indicate  85°  F.  on  a  hot  day,  little 
discomfort  follows;  but  let  the  humidity  rise  to  90  or  95  per 
cent,  while  the  temperature  remains  the  same,  and  oppres- 
sion, restlessness,  or  languor  results.  Much  the  same  effects 
are  seen  in  the  case  of  close  rooms  and  crowded  halls.     The 


air:    relation  to  human  life.  15 

watery  vapor  given  off  (about  20  grams  per  person  per  hour) 
soon  saturates  the  air,  and  the  consequent  drowsiness  and 
headache  usually  attributed  to  carbon  dioxide  will  be  felt; 
while  if  this  moisture  is  removed,  the  same  proportion  of 
carbon  dioxide  would  hardly  inconvenience  the  occupants. 
A  relative  humidity  of  60  per  cent,  is  said  to  be  the  most 
comfortable  for  house  temperature. 

In  normal  man,  exposure  to  cold  increases  the  respirator)" 
exchange;  but  if  he  represses  shivering  and  keeps  still  by 
force  of  will,  it  apparently  does  not.  Politely  sitting  still  in- 
creases the  probability  of  taking  cold.  A  high  temperature 
lessens  the  production  of  carbon  dioxide  and  therefore  saves 
food.  This  may  in  part  account  for  the  oppressiveness  felt 
by  well-fed  and  warmly  clothed  persons  in  public  places  none 
too  warm  for  those  with  a  more  restricted  diet. 

Muscular  activity  increases  respiratory  exchange  and 
causes  a  demand  for  food.  A  class  of  students  passing  across 
the  campus,  up  several  flights  of  stairs,  into  a  lecture-room 
vitiate  the  air  for  the  first  ten  minutes  at  a  rate  higher  by 
one  part  of  carbon  dioxide  per  10,000  than  half  an  hour  later. 
The  exchange  is  also  stimulated  by  a  meal.  Not  only  the 
oxidation  of  the  food  itself,  but  the  muscular  activity  of  the 
alimentary  canal  and  probably  other  accompanying  activities 
call  for  an  expenditure  of  energy  which  is  supplied  by  in- 
creased heat  production. 

Sodium  sulphate  is  said  to  increase  the  various  respira- 
tory activities,  and  some  have  held  this  fact  to  be  one  reason 
for  the  beneficial  effects  of  certain  mineral  waters. 

The  amount  of  carbon  dioxide  expired  is  estimated  by 
Pettenkofer  at  .006  to  .012  cubic  foot  per  pound  of  body 
weight,  according  to  the  degree  of  exertion.  Rubner  con- 
siders that,  in  general,  metabolic  processes  depend  also  upon 
the  proportion  of  superficial  area  to  the  total  volume  of  the 


l6  AIR,    WATER,    AND    FOOD. 

body,  hence  the  smaller  the  animal  the  greater  the  surface  to 
the  whole  mass.  Children  give  off  in  proportion  to  their 
body  weight  about  twice  as  much  carbon  dioxide  as  adults. 
Another  estimate  gives  the  output  of  carbon  dioxide  as 
.0027  gram  per  hour  per  square  centimeter  of  surface. 

Ammonia  is  also  a  constant  component  of  the  air  of  in- 
habited places  and  is  washed  out  by  rain  and  snow,  as  will 
be  shown  in  Chapter  VI. 

Of  the  occasional  impurities,  probably  the  most  fatal  is 
carbon  monoxide  arising  from  leaking  gas-fixtures  or  de- 
fective furnaces.  This  gas  has  250  times  the  affinity  for 
haemoglobin  and  therefore  forms  with  it  a  more  stable 
compound  than  does  oxygen,  and  hence  its  presence  causes 
a  deficiency  of  the  latter  gas  in  the  blood,  giving  symp- 
toms like  those  observed  in  mountain-climbing  or  bal- 
loon ascensions.  When  the  blood-corpuscles  become  about 
one-third  saturated  the  effect  becomes  sensible;  but  if  the 
quantity  of  gas  is  considerable,  the  symptoms  are  hardly 
noticeable  before  insensibility  occurs.  For  this  reason,  glow- 
ing charcoal  and  open  gas-jets  are  the  favorite  forms  of 
cowardly  self-destruction. 

In  the  neighborhood  of  factories,  smelting-works,  ore- 
heaps,  and  of  cities  burning  soft  coal  there  is  a  noticeable 
amount  of  sulphurous  and  sulphuric  acids,  sometimes  so  con- 
siderable as  to  destroy  vegetation. 

In  places  where  gas  is  burned,  oxides  of  nitrogen  are 
formed  in  small  quantity,  the  effect  of  which  is  known  to  be 
harmful.  Minute  quantities  of  hydrogen  sulphide  and  of  com- 
pounds of  carbon  and  hydrogen  and  of  other  gases  may  be 
present,  especially  in  houses  with  defective  plumbing  or  in  the 
neighborhood  of  barns,  cesspools,  and  filthy  back  yards. 
These  may  reach  dangerous  proportions,  but,  like  carbon 


air:    kkla'hon  to  human  life.  17 

monoxide,  should  not  be  permitted  in  or  near  any  well-regu- 
lated household. 

Soot,  being  insoluble,  accumulates  in  the  lungs,  as  a  post- 
mortem examination  of  persons  who  have  lived  for  some  tim  s 
in  a  smoky  city  proves;  nevertheless  no  definite  ill  effects 
have  been  as  yet  attributed  to  this  cause.  This  again  con- 
firms the  inference  that  it  is  the  gaseous  constituents,  and  the 
varying  temperature  and  pressure,  which  seriously  affect  the 
respiratory  exchange 

The  following  results,  obtained  on  the  air  of  a  large  man- 
ufacturing city,  will  be  of  interest  in  this  connection:  * 

GRAMS    PER     1,000,000    CUBIC    METERS    OF    AIR.f 

Soot.  HaS04.  FreeNHg.         Alb.  NH3.  HNO,.  HNOj. 

1000  to  40000      7000  to  63000'      100  to  1000       97  to  557       45  to  1063       O  to  155. 

»  Partly  HjSOa. 

It  is  probable  that  much  of  the  danger  ascribed  to  sewer- 
air  arises  from  other  causes.  Since  the  atmosphere  in  sewer- 
pipes  is  always  moist,  the  only  probable  source  of  organisms. 
is  the  splashing  of  the  water.  Only  about  one-half  as  many 
organisms  have  been  found  in  the  air  above  flowing  sewage 
as  in  out-door  air.  Professor  Carnelley  and  Dr.  Haldane 
found  only  one-half  as  much  carbon  dioxide  and  one-third 
as  much  organic  matter  in  such  air  as  in  that  of  the  str^^ets. 
above. 

Beyond  individual  control,  and  in  a  measure  beyond  gen-^ 
eral  control,  there  exists  suspended  matter  in  the  air:  fine 
volcanic  dust,  pollen,  spores  of  moulds  and  algae,  dried  bac- 
teria, diatoms,  small  seeds  of  plants,  soot  and  the  finely 
pulverized  earth  from  roads  and  cultivated  and  barren  lands. 
To  this  portion  of  the  air  we  owe  beautiful  sunsets  and  d*'^- 
agreeable  fogs.     To  it  many  aflfections  of  the  throat  and 

*  Mabery:   /.  .^m.  Chem.  Sor.,  17  f/<?95)    105. 

f  See  also  Bailey:  "  The  Air  of  Large  Towns,"  Science,  Oct.  13,  1893. 
Irwin:  "The  Soot  Deposited  on  Manchester  Snow,"/.  Soc.  Chem.  Ind^ 
U9o^),  533. 


1 8  AIR,    WATER,    AND    FOOD. 

-eyes  are  due,  and  by  it  disease  may  be  transmitted.  Some 
kinds  of  dust  lodge  in  the  air-cells  and  by  irritation  render 
tke  individual  liable  to  disease,  as  statistics  of  the  mortality 
'A  dust-producing  trades  show.  In  the  air  of  houses  this 
impurity  increases  a  thousand-fold  by  means  of  the  wear  of 
furnishings  and  the  accumulation  on  them  of  deposited  par- 
tlcies,  by  means  of  furnace-ashes  and  dried  debris  of  all 
kinds.  Only  recently  have  the  dangers  of  this  part  of  the 
air  we  breathe  been  distinctly  pointed  out. 

Aitken  *  estimated  that  a  cubic  inch  of  air  may  carry 
2000  dust-particles  in  the  open  country,  3,000,000  and  more 
in  cities,  and  30,000,000  in  inhabited  rooms.  Among  these 
millions  there  may  be  found  from  ten  to  several  hundred 
micro-organisms,  moulds,  and  bacteria,  and,  under  certain 
conditions,  pathogenic  germs. 

As  methods  of  culture  become  more  satisfactory  and  tests 
more  universal,  it  may  be  demonstrated  that  many  old  or 
long-inhabited  buildings  furnish  several  varieties  of  patho- 
genic germs  constantly  to  the  air. 

According  to  some  authorities,  the  most  dangerous  con- 
tamination of  the  air  is  the  "  crowd-poison,"  or  organic 
matter  given  oflf  with  the  carbon  dioxide  and  moisture  in  the 
breath.  References  will  be  found  in  the  bibliography  to  dis- 
cussions of  the  subject.  No  evidence  has  ever  been  found 
in  the  course  of  investigations  in  tiiis  laboratory,  covering  a 
period  of  twenty-live  years,  that  the  healthy  humsin  lung  gives  off 
any  toxic  substance.  The  same  conclusion  is  reached  by  Dr. 
Emanuel  Formanek  of  the  Hygienic  Institute  at  Prague  after 
a  long  series  of  critical  experiments.! 

*  Nature,  31  {1870)^  265;  41  {iS8d),  394. 
•j-  Archiv  fur  Hygiene,  38(/900),  i. 


CHAPTER  III. 

THE    PROBLEM    OF    VENTILATION. 

From  the  preceding  chapter  it  will  be  seen  how  impor- 
tant is  the  purity  of  the  air  to  human  well-being,  and  how 
essential  is  the  diffusion  of  the  knowledge  of  the  methods 
by  which  it  can  be  secured.  It  is  often  said  that  artificial 
ventilation  is  a  modern  necessity.  Remains  of  aqueducts 
and  sewers  have  testified  to  the  sanitary  intelligence  of  his- 
toric peoples,  but  the  ventilating  fan  does  not  seem  to  have 
been  included,  although  natural  ventilation  by  shafts  and  flues 
has  been  practised  since  man  came  out  of  cave-dwellings.  It 
is  true  that  customs  have  changed  as  to  many  items  of  daily 
life.  In  cities  more  people  live  on  an  acre  of  ground,  thus 
fouling  the  air  above  and  the  ground  beneath;  more  factories 
are  belching  smoke;  more  coal  is  burned;  houses  are  built 
with  smaller  rooms  and  less  pervious  walls;  schools  and 
lecture-halls  are  more  crowded;  people  are  better  fed,  con- 
sequently there  is  more  garbage;  streets  are  macadamized, 
allowing  finely  ground  particles  to  fill  the  air  with  every  puff 
of  wind;  gas-pipes  traverse  the  walls  of  every  house  and 
pass  under  every  street;  carpets,  draperies,  and  much  passing 
in  and  out  cause  an  accumulation  of  dust  unknown  fifty 
years  ago.  Kerosene  lamps  require  more  oxygen  than  many 
candles.  Besides,  people  are  becoming  less  hardv  and  more 
sensitive  physically,  so  that  well-ventilated  living-spaces  are 
a  modern  necessity  if  human  efficiency  is  to  be  maintained. 

19 


20  AIR,    WATER,    AND    FOOD. 

As  we  have  seen,  the  air  of  open  spaces  presents  only 
very  sHght  variation  at  the  same  level  or  for  several  thousand 
feet  above  it.  The  movement  of  the  air  caused  by  the  wind 
is  usually  so  rapid,  and  the  reservoir  of  air  for  many  miles 
above  the  earth  is  so  immense  in  comparison  with  the  thin 
vitiated  layer,  that  there  are  only  to  be  considered  enc'osed 
spaces  in  which  human  beings  remain  for  a  period  of  time. 

To  supply  the  7000  to  12,000  liters  (250  to  430  cub  c  feet) 
of  tidal  air  per  person  in  maximum  purity,  there  must  be 
brought  to  the  person  at  rest  some  1800  cubic  feet  of  air  per 
hour.  If  he  were  in  an  air-tight  chamber  12  feet  square  and 
8  feet  high,  a  man  would  reach  the  limit  of  purity  in  38 
minutes;  but  no  ordinary  room  is  air-tight,  and  when  the 
difference  between  inside  and  outside  temperature  is  consid- 
erable, a  rapid  exchange  is  taking  place  even  with  doors  and 
windows  shut. 

To  secure  the  passage  of  this  large  volume  of  air  through 
a  small  space  without  causing  a  draft  that  will  be  objected  to 
by  the  abnormally  sensitive  victim  of  modern  luxurious 
habits  is  the  problem  of  ventilation — one  not  yet  satisfactorily 
solved. 

The  sanitary  engineer  is  expected  to  design  the  appara- 
tus and  to  aid  the  architect  in  so  placing  and  proportioning 
flues,  inlets,  and  outlets  as  to  accomplish  the  desired  results. 
Unfortunately  it  is  too  common,  especially  in  the  case  of 
school  and  college  buildings,  to  economize  in  the  first  cost 
by  dispensing  with  the  services  of  the  expert  and  to  leave  to 
the  builder  and  *'  practical  "  architect  all  such  details.  In 
any  case,  it  often  becomes  necessary  to  call  in  the  chemi^^t  to 
prove  the  need  of  reform,  or  to  show  by  the  compositi  ^n  of 
the  air  whether  or  not  the  ventilating  plant  is  doing  i*^s  w^rk 
efficiently. 

The  sanitary  inspector,  whose  business  it  is  to   decide 


air:     THK    problem    of    ventilation.  21 

upon  the  legal  questions  connected  with  tenements  and  fac- 
tories, must  often  rely  upon  chemical  examinations  of  the 
air.  The  validity  of  these  depends  not  only  upon  the  per- 
fection and  delicacy  of  apparatus  and  methods  used,  but  also 
upon  the  judgment  and  intelligence  with  which  the  samples 
are  taken. 

Many  errors  in  the  construction  of  buildings  have  been 
perpetrated  because  of  an  ignorance  of  the  physical  proper- 
ties of  air  and,  consequently,  a  mistaken  notion  of  the  be- 
havior of  a  vitiated  atmosphere.  The  lecturer  on  popular 
science  who  some  forty  years  ago  enlightened  (?)  the  com- 
munity on  the  chemistry  of  daily  life  was  accustomed  to  use, 
as  a  striking  illustration,  a  glass  jar  in  which  a  small  lighted 
candle  was  instantly  extinguished  on  pouring  into  the  jar  a 
tumblerful  of  carbon  dioxide  which  had  been  collected  for 
the  purpose.  The  inference  was  plain:  carbon  dioxide  was 
heavier  than  air,  therefore  it  falls  to  the  floor  and  must  be 
allowed  to  flow  out  as  if  it  were  a  stream  of  w^ater.  Further 
confirmation  of  this  inference  was  found  in  the  frequently 
observed  fact  that  a  candle  lowered  into  a  well  often  went 
out  just  before  the  w^ater  was  reached. 

Hence  for  many  years  the  habits  of  thoughtful  persons 
Avere  formed  on  a  belief  in  the  heaviness  of  carbon  dioxide  or 
*'  bad  air,"  and  in  its  tendency  to  go  to  the  bottom  of  the 
room  and  into  any  holes  it  could  find.  This  is  only  another 
instance  of  danger  in  half  a  truth.  When  do  we  find  cold 
carbon  dioxide  generated  in  living-rooms?  And  how  warm 
must  the  gas  be  in  order  to  be  lighter  than  the  ordinary  air? 
How  quickly  does  diffusion  take  place?  Until  within  a  very 
few  years  the  almost  unanimous  belief  among  the  so-called 
educated  classes  was  that  the  bad  air  could  be  let  out  by 
opening  a  window  at  the  bottom,  and,  in  spite  of  the  lessons 
ivhich  might  have  been  learned  by  any  observant  person  in 


22  AIR,    WATER,    AND   FOOD. 

hanging  pictures  or  Christmas  greens,  the  common  practice 
in  private  houses,  churches,  and  schools  is  to  open  the  win- 
dows at  the  bottom. 

All  ordinary  vitiation  of  the  air  proceeds  from  a  heated 
source.  Human  breath  and  warm  air  are  lighter  than  cold 
air  and  rise  even  with  their  burden  of  carbon  dioxide.  It  is 
only  when  they  impinge  on  a  very  much  colder  surface,  as  on 
the  window-pane  on  a  very  cold  day,  that  they  become  suffi- 
ciently chilled  to  fall  without  mixing  with  the  neighboring" 
air.  The  freedom  with  which  the  gases  of  the  air  mix,  as 
well  as  the  rapidity  of  the  action,  may  be  illustrated  in  a 
variety  of  ways.  Open  a  bottle  of  any  volatile  and  pungent 
substance,  as  ammonia  or  hydrogen  sulphide,  in  one  corner 
of  a  room,  and  almost  instantly  it  may  be  perceived  in  the 
most  distant  part. 

In  natural  ventilation  we  have  only  to  avail  ourselves  of 
these  characteristic  properties  of  gases;  and  whether  we  wish 
to  get  rid  of  the  light  gases  escaping  from  furnace,  stove,  or 
gas-pipe,  or  of  the  specifically  heavier  carbon  dioxide,  or  of 
the  most  dangerous  dust,  we  must  furnish  an  outlet  at  the 
place  to  which  the  fleeing  enemy  first  arrives,  lest  it  turn  and 
rend  us  for  our  ignorance. 

It  is  usually  sufficient  to  furnish  this  opportunity,  the 
current  caused  by  this  willing  escape  drawing  in  sufficient 
fresh  air  to  take  its  place  except  in  very  crowded  rooms,  and 
even  these  might  be  so  ventilated  provided  the  whole  roof 
were  one  large  ventilating  flue.  If,  however,  the  air  is  to  be 
drawn  from  the  bottom  of  the  room,  its  unwilling  current 
must  be  pulled  by  a  superior  force,  as  by  an  open  fire  on  the 
hearth,  which  heats  the  air  above  it  so  that,  in  rushing  into 
the  free  air  above,  it  draws  after  it  all  things  movable  within 
reach.  Then,  indeed,  even  the  top  of  the  room  becomes 
quickly  cleared  and  no  corner  can  escape;   but  if  the  fire  be 


AIR:     THE    PROBLEM    OF    VENTILATION.  23' 

long  gone  out  and  the  chimney  cold,  the  reverse  takes  place 
and  cold,  heavy  air  sinks  to  the  floor,  helping  to  confine  the 
bad  air  at  the  top  of  the  room. 

What  the  cold  chimney  cannot  accomplish  the  mechani- 
cally driven  fan  can  do,  namely,  by  a  slight  compression 
force  a  draught  even  up  a  cold  chimney.  In  this  case  the 
very  unwillingness  of  the  air  to  take  the  prescribed  path 
helps  in  the  result  as  water  forced  through  a  mill-wheel  de- 
velops mechanical  work.  The  warmed  fresh  air  forced  in 
near  the  top  of  the  room  loses  its  velocity  as  it  mingles  with 
that  already  present,  and  finds  its  way  along  the  line  of  least 
resistance  to  the  opening  provided  at  the  bottom  of  the 
room,  into  the  flue,  but  only  in  case  there  is  no  easier  way. 

Open  doors  or  windows  interfere  with  the  prescribed 
course,  and  blindness  to  this  fact  on  the  part  of  the  occupants 
of  mechanically  ventilated  buildings  has  caused  unjust  com- 
plaints of  the  system.  The  necessity  of  regulating  the  con- 
sumption of  fuel  and  admission  of  fresh  air  in  accordance 
with  variations  of  temperature,  as  well  as  the  great  care  and 
trouble  this  involves,  renders  the  ''  natural  "  system  of  ventila- 
tion practicable  only  in  less  crowded  dwelling-houses  where 
intelligence  can  control  the  varying  factors.  For  schools, 
lecture-halls,  or  any  enclosed  spaces  occupied  by  numbers  of 
persons  at  one  time,  some  form  of  mechanical  ventilation 
ofYers  the  only  hope  of  good  air  in  cold  climates.  What 
form  that  shall  take  is  for  the  engineer  to  decide.  The  chem- 
ist's part  is  to  devise  means  of  readily  determining  whether 
the  persons  in  charge  of  the  apparatus  are  using  it  to  gain 
the  results  designed  by  the  expert. 

As  a  test  of  how  nearly  practice  approaches  the  theoreti- 
cal value,  carbon  dioxide  is  taken  as  the  indicator,  since  it  is 
present  in  a  thousand  times  larger  quantity  than  any  other 
impurity  and  since  it  is  easily  determined.     If  the  air  has 


24  AIR.    WATER,    AND    FOOD. 

only  the  normal  amount  of  carbon  dioxide,  it  is  but  rarely 
that  it  contains  enough  of  anything  else  to  be  harmful.  The 
presence  of  hydrogen  sulphide  or  of  coal-gas  is  betrayed  by 
the  odor.  Where  the  gas-supply  is  ''  water-gas,"  contain- 
ing 30  to  40  per  cent,  of  carbon  monoxide,  there  is  greater 
danger;  but  if  legal  restrictions  are  complied  with,  the  pres- 
ence of  this  can  be  detected  in  the  same  way,  viz.,  by  the 
odor. 

Danger  may  also  arise  from  the  presence  of  so-called 
''  sewer-gas,"  which,  however,  is  not  a  single  gas,  but  a  most 
complex  and  variable  mixture  of  the  more  volatile  products 
of  decomposition.  For  the  detection  of  **  sewer-air  "  chemi- 
cal tests  are  of  little  value,  since  it  contains  no  constituent 
in  suf^cient  quantity  and  with  sufificient  regularity  to 
serve  as  an  index  of  its  presence.  Ill-smelling  gases  are 
given  off  only  when  sewage  is  about  eighteen  hours  old, 
hence  dirty  house-pipes  are  the  chief  cause  of  foul  air.  The 
delicate  sense  of  smell  is  of  value  here.  Indeed,  an  edu- 
cated nose  is  most  essential  in  all  examinations  of  house- 
air.  "  Crowd-poison,"  if  it  exists,  keeps  company  with  the 
increase  of  the  products  of  respiration,  and  if  the  incoming 
air  is  strained  or  taken  from  a  place  free  from  dust,  the  par- 
ticles added  to  the  air  which  is  in  the  rooms  will  also  be  re- 
moved with  the  carbon  dioxide. 

From  nearly  all  points  of  view,  carbon  dioxide  is  an  indi- 
cator of  the  efificiency  of  ventilation,  especially  if  combined 
with  observations  of  temperature  and  moisture.  It  is  an  in- 
dicator also  readily  understood  and  accepted  by  the  public. 

The  principles  of  ventilation  may  be  readily  illustrated  to 
a  class  by  means  of  simple  apparatus.  Such  an  apparatus, 
using  candles  and  designed  to  illustrate  the  section  of  an 
ordiriarv  room,  is  shown  in  Fig.  I. 

In  testing  the  efficiency  of  ventilation  of  any  room  or 


air:    the  problem  of  ventilation. 


5 


building,  it  is  necessary  to  determine  first  the  direction  of  the 
air-currents,  for  there  can  be  no  ventilation  without  currents. 
If  the  architect  who  designed  the  building,  or  the  engineer 
who  advised  the  architect,  is  responsible,  then  the  chemist 
has  only  to  follow  directions  in  taking  the  samples;  but  fre- 
quently the  chemist,  as  well  as  the  sanitary  engineer,  is  called 


Fig.  I. — Apparatus  to  Illustrate  the  Principles  of  Ventilation. 

Upon  to  make  tests  of  rooms  and  buildings  of  which  no  plans 
are  available. 

In  the  examination  of  such  rooms,  then,  the  position  of 
flues  or  conduits,  both  inlets  and  outlets,  which  were  intended 
to  convey  air  or  which  serve  without  such  intention,  should 
first  be  located.  Possible  avenues  of  ingress  and  egress  by 
means  of  loose  windows,  cracks  around  doors,  etc.,  are  to  be 
considered.  When  there  is  great  difference  of  temperature 
between  outer  and  inner  air,  these  allow  of  quite  rapid  change 
of  air.  Some  means  of  rendering  visible  these  currents  is  de- 
sirable, such  as  smouldering  paper,  magnesium  powder,  or 
fumes  of  ammonium  chloride. 


26  AIR,    WATER,    AND    FOOD. 

When  the  direction  and  intensity  of  these  air-currents 
have  been  determined,  the  places  from  which  the  air-samples 
are  to  be  taken  may  be  chosen.  It  will  be  evident  in  what 
part  of  the  room  stagnation  occurs  and  where  eddies  are 
formed,  also  where  the  air  escapes. 

In  a  room  or  building  without  artificial  ventilation  the 
air-currents  are  seen  to  be  ascending  until  they  become 
chilled,  when  they  fall.  An  empty  room  will  not  show  so 
decidedly  the  rise  of  air-currents  as  will  an  occupied  one  in 
which  the  vitiated  air,  being  much  warmer,  rises  more  rap- 
idly and  cools  less  quickly.  In  taking  the  samples  all  acci- 
dental means  of  contamination  must  be  avoided  and  the 
occupants  must  be  quiet,  for  the  moving  of  persons  causes 
disturbance  in  the  air-current.  There  is  room  for  great  in- 
genuity in  this  part  of  the  examination,  as  circumstances 
greatly  modify  the  method  of  procedure.  A  fair  sample,  or 
a  sufftcient  number  of  samples  to  give  a  fair  average,  must 
be  taken. 

Having  secured  and  analyzed  the  samples  of  air,  the  de- 
cision as  to  the  efificiency  of  ventilation  must  be  rendered. 

If  the  room  examined  is  a  study-  or  recitation-room,  the 
stratum  of  air  at  the  level  of  the  students'  heads  should  not 
contain  over  8  or  9  parts  per  10,000  of  carbon  dioxide,  should 
not  show  a  temperature  of  over  70°  F.,  nor  a  humidity  of 
over  35  or  50  per  cent.,  and  these  conditions  should  be  main- 
tained for  hours  at  a  time. 

For  lecture-halls  and  spaces  occupied  for  only  one  hour 
at  a  time,  with  ample  time  between  occupation,  it  is  admis- 
sible to  allow  9  to  II  parts.  If  fan  ventilation  is  used,  the 
outlet  should  give  the  average  degree  of  contamination.  If 
no  system  is  used,  the  air  at  the  top  of  the  room  is  first 
vitiated;  only  at  the  end  of  twenty  minutes  to  half  an  hour 
do  the  lower  layers  begin  to  show  it. 


CHAPTER  IV. 

ANALYTICAL     METHODS.        DETERMINATION    OF    CARBON 

DIOXIDE. 

General  Statements. — Since  the  earliest  crude  attempts 
at  the  determination  of  carbon  dioxide  all  chemical  methods 
have  been  based  on  its  absorption  by  alkalies  or  alkaline 
earths.  It  may  be  the  diminution  in  volume  of  the  air 
through  absorption  of  the  carbon  dioxide  that  is  measured ; 
the  carbon  dioxide  may  be  separated  as  barium  carbonate 
and  weighed;  the  reduced  alkalinity  of  the  absorbing  liquid 
may  be  determined ;  or  the  carbon  dioxide  may  be  set  free 
from  the  absorbing  solution  and  its  volume  determined 
directly ;  all  of  these  methods  have  been  used  with  more  or 
less  success.  For  determining  with  great  exactness  the 
amount  in  out-door  or  "  fresh  "  air  it  is  customary  to  aspirate 
large  quantities  of  air,  sometimes  as  much  as  600  liters, 
through  the  absorbing  solution.  For  determining  the 
amount  in  the  air  of  rooms  a  much  smaller  sample,  collected 
in  calibrated  vessels,  of  from  one  to  eight  liters,  is  preferable. 

Where  it  is  necessary  to  absorb  large  quantities  of  the 
gas  in  a  slight  volume  of  solution,  potassium  or  sodium  hy- 
droxide is  used.  For  nearly  all  of  the  ''  popular  tests  "  cal- 
cium hydroxide,  lime-water,  is  used  because  of  its  harmles$ 
nature  and  the  ease  with  which  it  can  be  obtained  from  the 
comer  drug  store,  or  from  the  quicklime  procured  from  the 
mason's  barrel.  For  volumetric  methods  barium  hydroxide 
is  generally  preferred,  because  of  the  less  solubility  of  the 

27 


28  AIR,    WATER,    AND    FOOD. 

barium  carbonate,  it  being  only  about  two-thirds  as  soluble 
as  the  calcium  salt.  The  very  avidity  with  which  these 
substances  take  up  carbon  dioxide  is  a  hindrance  to  the 
preparation  of  standard  solutions  in  an  atmosphere  already 
rich  in  it.  When  once  prepared  the  solution  must  be  pre- 
serv^ed  with  especial  care,  since  contact  with  the  hands  or  a 
whiff  of  the  breath  will  reduce  its  strength  and  vitiate  the 
results.  All  such  solutions  are  best  kept  in  bottles  well  pro- 
tected from  the  air  by  tubes  filled  with  soda-lime  and  de- 
livered from  a  burette,  as  described  on  page  36. 

Pettenkofer  Method. — The  method  which  for  many  years 
was  generally  employed  for  the  estimation  of  carbon  dioxide 
in  the  air  of  rooms  is  some  modification  of  that  originally 
devised  by  Pettenkofer.* 

Principle. — In  principle  this  consists  in  absorbing  the 
carbon  dioxide  from  a  known  volume  of  air  in  barium  hy- 
droxide solution  and  titrating  the  excess  with  standard 
sulphuric  acid.  It  is  essential  for  the  complete  absorption  of 
the  carbon  dioxide  that  the  barium  hydroxide  be  largely  in 
excess,  so  that  not  more  than  one-fifth  of  it  is  neutralized; 
furthermore,  the  absorbing  solution  must  be  shaken  up  with 
the  air  for  a  considerable  time. 

Collecting  the  Samples.^The  samples  are  collected  in  four- 
or  eight-liter  bottles,  the  volume  of  which  is  accurately 
known,  the  bottles  having  been  calibrated  by  weighing  them 
filled  with  water.  These  bottles  are  provided  with  a  rubber 
stopper  carrvang  a  glass  tube  over  which  a  rubber  nipple 
is  slipped.  They  are  filled  with  the  air  to  be  tested  by 
means  of  a  pair  of  nine-inch  blacksmith's  bellows,  fitted 
with  valves  so  arranged  as  to  draw  the  air  cut  of  the  bcttle. 
The  bellows  is  connected  with  a  three-quarter-inch  brass 


*  Pettenkofer:  Annolen,  2,  Supp.  Band  {1862),  p.  i.     Gill:  Analyst,  17  {i8q2\ 


air:  analytical  methods.  29 

tube  reaching  nearly  to  the  bottom  of  the  bottle ;  fifteen  or 
twenty  strokes  should  be  sufficient  to  replace  the  air  in  a 
four-liter  bottle.  At  the  time  of  collecting  the  samples  the 
following  observations  should  be  recorded :  Room ,  date, 
time,  weather,  place  in  room,  number  of  people  present,  number 
of  gas-jets  or  lamps  burning,  condition  of  the  doors,  windows, 
and  transoms;  in  short,  everything  that  would  tend  to  affect 
the  amount  of  carbon  dioxide  in  the  air,  or  to  cause  currents  or 
eddies.  The  bottles  should  be  distinctly  labelled  and  their 
volumes  recorded.  If  the  temperature  at  the  point  where 
the  samples  are  collected  should  be  essentially  different  from 
that  of  the  laboratory,  the  bottles  should  be  allowed  to 
stand  in  the  laboratory  for  half  an  hour,  or  until  they  have 
attained  its  temperature. 

Directions  for  Laboratory  Work, — The  solutions  of  barium 
hydroxide  and  sulphuric  acid  which  are  used  are  approxi- 
mately of  equal  strength;  but  since  it  is  impracticable  to 
prepare  exact  solutions  of  barium  hydroxide  and  to  keep 
them  without  change,  the  exact  value  of  the  barium  hy- 
droxide solution  must  be  found  by  titration  against  the 
standard  sulphuric  acid,  which  is  made  of  such  a  strength 
that  I  cubic  centimeter  is  equivalent  to  exactly  i  milligram 
of  COj.  This  standardization,  as  well  as  the  subsequent 
titration,  is  best  made  in  a  small  flask  to  lessen  the  error 
from  absorption  of  carbon  dioxide  from  the  air.  It  will  be 
found  most  generally  satisfactory  to  measure  into  the  flask 
about  25  c.c.  of  the  barium  hydroxide,  add  a  drop  of  phen- 
olphthalein  solution,  and  titrate  with  the  sulphuric  acid  to 
the  disappearance  of  the  pink  color.  In  all  cases  the  first 
end-point  should  be  taken  as  the  correct  one,  because  the 
pink  color  will  sometimes  return  on  standing.  This  is  due 
to  the  presence  of  minute  quantities  of  potassium  or  sodium 
hy^ri'^ide  in  the  solution.     The  alkali  sulphates  will  react 


30  AIR,    WATER,    AND    FOOD. 

with  any  barium  carbonate  which  may  be  suspended  in  the 
Hquid  with  the  formation  of  alkaH  carbonates  which  give  a 
pink  color  with  phenolphthalein.*  The  standardization 
should  be  repeated  until  consecutive  results  are  obtained 
which  check  within  0.2  per  cent,  of  each  other. 

Determination. — Remove  the  cap  from  the  tube  in  the 
stopper  of  the  bottle,  insert  the  tube-tip  of  the  burette  so 
that  it  projects  into  the  bottle,  and  run  in  rapidly  50  c.c  of 
barium  hydroxide  from  the  burette.  Replace  the  cap  and 
spread  the  solution  completely  over  the  sides  of  the  bottle 
while  waiting  three  minutes  for  the  burette  to  drain.  In 
doing  this  take  care  that  none  of  the  solution  gets  into  the 
cap.  Note  carefully  the  temperature  and  barometric 
pressure.  Place  the  bottle  on  its  side  and  roll  or  shake  it 
at  frequent  intervals  for  forty-five  minutes,  taking  care  that 
the  whole  surface  of  the  bottle  is  moistened  with  the  solution 
each  time.  At  the  end  of  this  time  thoroughly  shake  the 
bottle  to  mix  the  solution,  remove  the  cap,  and  pour  the 
solution  into  a  stoppered  bottle  of  hard  glass  of  40  c.c. 
capacity,  taking  care  that  the  solution  shall  come  in  contact 
with  the  air  as  little  as  possible.  Under  these  conditions  a 
full  well-stoppered  bottle  may  safely  stand  for  days  before 
titration.  For  the  titration,  measure  out  with  a  pipette 
25  c.c.  of  the  clear  liquid  into  a  75-c.c.  flask  and  titrate  it 
with  the  sulphuric  acid  as  in  the  standardization.  The  differ- 
ence between  the  number  of  cubic  centimeters  of  standard 
acid  required  to  neutralize  the  total  barium  hydroxide 
before  and  after  absorption  gives  the  number  of  milligrams 
of  dry  carbon  dioxide  in  the  sample  tested.  The  results 
may  be  expressed  in  parts  per  10,000,  by  volume,  under 

*  This  action  can  be  largely  prevented  by  including  a  small  amount  of  barium 
chloride  when  making:  up.  the  barium  hydroxide  solution  (see  p.  247.) 


air:  analytical  methods.  31 

standard  conditions  (0°  and  760  mm.),  saturated  with 
moisture  (Method  i)  or  dry  (Method  2).  Tables  for  this 
purpose  will  be  found  in  Appendix  A.* 

Example. — Data:  Standardization,  I  c.c.  Ba  (0H)2  = 
1.020  c.c.  H2SO4  volume  of  bottle  =  8490  c.c;  Ba(OH)^ 
used  =  49.9  c.c.  ;  H2SO4  used  =  21.1  c.c.  ;  temperature  and 
pressure  =  21°  and  'j(:)(^  mm. 

Before  absorption 

49.9  c.c.  Ba(0H)2  =  49.9  X  1.020  =  50.90  c.c.  H2SO4. 

After  absorption 

4Q.0 
49.9  c.c.  Ba(0H)2  =  ^^^  X  21. 1   =  42.12  c.c.  H2SO4. 

.  *.  (8490  —  49.9)  =  8440. 1  c.c.  air  contain  50.90 — 42. 12  = 
8.78  mg.  CO2. 

Method  I. — I  c.c.  CO2  saturated  with  moisture  at  21°  and 
'jd^  mm.  weighs  1.79624  mg.  (Table  II,  Appendix  A). 

.-.   8.78  mg.  =        '  . —  =4.887  c.c.   CO2  saturated  with 

moisture. 

A  887 
Hence  in  10,000  c.c.  of  air  there  are  ^ — —   X   10,000  = 

8440. 1 

$.79  parts  CO2. 

Method  2. — In  this  method  the  volume  of  air  is  reduced 
to  standard  conditions  of  temperature  and  pressure,  under 
which  conditions  the  weight  of  a  cubic  centimeter  of  dry  CO2 
is  a  constant  quantity. 

Thus  v'  =  v\\  +  o.oo366(/'  —  r)].  v'  =  8440.1,  f  =  21°, 
f  —  0°;  hence  v  —  7837.7  c.c. 

*  Dietrich's  Table,  the  one  in  general  use,  is  not  absolutely  correct,  the 
weight  of  a  cubic  centimeter  of  carbon  dioxide  at  o"  C.  and  760  mm.  being 
somewhat  different  from  that  given  at  present  by  the  best  authorities,  but 
it  is  sufficiently  close  for  any  but  the  most  exacting  work. 


32  AIR,    WATER,    AND    FOOD. 

Also,   V  :  v"=H"'.H,  or    ^ZiJ.']  :  ;ir=76o:  (766- 18.5). 

(18.5  =  tension  aqueous  vapor  at  2I°.) 

Then  v"  =  7709  c.c.  =  volume  of  air  at  0°  and  760  mm. 

I  c.c.  CO2  at  0°  and  760  mm.  weighs  1.9643  mg. 

8.78  4.460 

=  4.469  c.c.  CO2. ~  X  10,000  =5.79  parts 


1.9643       ^^  "^  7709 

CO2  per  10,000. 

Two  samples  are  to  be  taken,  closely  following  the  notes, 
and  the  results  calculated  by  both  methods  before  collecting 
more  samples.  Then  some  one  room  may  be  taken  and  the 
quality  of  the  air  determined  for  the  different  hours  of  the 
day,  or  a  comparison  of  dififerent  rooms  may  be  made,  or  a 
building  may  be  tested  as  a  whole.  All  data  and  results  ob- 
tained should  be  arranged  in  tabular  form  on  a  separate  page 
of  the  note-book. 

Notes. — This  method  of  collecting  the  air  in  a  large  bottle 
possesses  a  decided  advantage  over  the  method  of  slowly 
drawing  the  air  through  barium  hydroxide  contained  in  a  long 
tube,  in  that  a  sample  represents  the  condition  of  the  air  at 
a  given  time  and  not  its  average  condition  for  a  period  of  an 
hour  or  so. 

In  collecting  samples,  care  must  be  taken  to  avoid  cur- 
rents of  air  or  the  close  proximity  of  people.  Duplicate 
samples  can  be  obtained  only  in  empty  or  nearly  empty 
rooms.  Even  two  sides  of  the  same  room  will  probably 
show  differences,  but  two  samples  taken  carefully  side  by 
side  ought  to  agree  within  0.05  part  per  10,000. 

While  the  Pettenkofer  method  is  convenient,  and  for  a 
long  time  has  been  the  favorite,  it  is  now  quite  generally 
recognized  that  it  contains  inherent  sources  of  error  which 
can  be  obviated  only  by  the  use  of  complicated  apparatus 
and  extreme  skill  in  manipulation.  That  the  method  can 
be  employed  to  obtain  results  of  the  highest  degree  of  accu- 


AIR:    ANALYTICAL    METHODS.  33- 

racy  has  been  shown  by  Letts  and  Blake*  in  an  exhaustive 
study  of  the  question.  The  refinements  found  necessary, 
however,  place  their  modification  out  of  consideration  for 
ordinary  use. 

The  principal  source  of  error  lies  in  the  necessity  for 
titrating  the  alkaline  liquid  within  the  "area  of  contamina- 
tion," the  exhaled  breath  containing  on  an  average  from 
50  to  100  times  as  much  carbon  dioxide  as  the  air  under 
examination.  Other  important  sources  of  error  which  have 
been  found  to  lead  to  erroneous  results  are  the  action  of 
the  caustic  alkali  on  the  glass  of  the  large  bottle,  and  the 
presence  of  small  amounts  of  the  precipitated  barium  car- 
bonate in  the  solution  during  the  titration.  It  should 
therefore  be  borne  in  mind  that  results  obtained  by  this 
method  may  be  too  high  even  though  agreeing  closely 
among  themselves. 

The  small  bottle  to  which  the  solution  is  transferred  for 
settling  should  be  of  such  a  size  (40  c.c.)  that  the  volume 
which  drains  readily  from  the  large  bottle  when  the  glass 
tube  is  flush  with  the  stopper  shall  a  little  more  than  fill  it. 
That  is,  no  air-space  should  be  left  to  serve  as  a  medium  for 
transpiration  from  the  surrounding  air  if  the  bottle  stand 
for  some  hours.  On  the  other  hand,  there  should  be  a 
sufficient  excess  over  the  25  c.c  needed  to  ensure  the  fillmg^ 
of  the  pipette  at  the  first  trial.  This  pipette  is  globular  in 
shape,  with  a  stem  of  small  diameter  above  and  below  the 
bulb.  The  last  drop  is  taken  off  by  touching  the  neck 
of  the  flask  after  counting  ten  from  the  time  it  is 
empty.  It  is  then  set  upright  to  drain;  the  drop  which 
collects  is  gently  shaken  out  before  the  next  titration. 
The  error  is  less  than  if  it  were  rinsed  with  water  each  time. 

All  rubber  stoppers  which  are  used  should  first  be  boiled 

*  Proc.  Royal  Dublin  Soc.,  g,  107  {igoo). 


34  AIR,    ^VATER,    AND    FOOD. 

in  dilute  caustic  soda,  then  in  a  dilute  solution  of  potassium 
bichromate  and  sulphuric  acid  and  thoroughly  washed. 

Walker  Method. ^A  comparatively  simple  method  in 
which  the  errors  inherent  to  the  Pettenkofer  process  are 
•avoided  has  been  proposed  by  Walker.* 

The  method  has  been  carefully  studied  in  this  laboratory  f 
and  found  to  be  capable  of  great  accuracy 

Principle. — To  a  definite  volume  of  air,  usually  i  to  2 
Hters,  is  added  a  measured  amount  of  standard  barium 
hydroxide,  care  being  taken  to  avoid  contact  of  the  solution 
Avith  the  air.  After  the  absorption  of  the  carbon  dioxide, 
the  solution  is  filtered  under  reduced  pressure  through  as- 
bestos and  the  clear  barium  hydroxide  received  into  a 
known  excess  of  standard  hydrochloric  acid.  The  absorp- 
tion vessel  is  rinsed  out  with  water  free  from  carbon  dioxide. 
The  excess  of  acid  is  then  determined  by  titration  with 
barium  hydroxide. 

Reagents  and  Apparatus. — The  standard  solutions  used 
•are  N/50  hydrochloric  acid,  and  barium  hydroxide,  approxi- 
mately N/ioo,  its  exact  strength  relative  to  the  acid  being 
found  daily  by  titration.  It  will  be  found  advantageous 
to  use  solutions  of  this  strength,  somew^hat  more  dilute  than 
those  recommended  by  Walker,  on  account  of  the  increased 
accuracy  with  air  nearly  free  from  carbon  dioxide.  The 
decreased  range  of  usefulness  is  readily  compensated  by 
the  employment  of  smaller  samples  of  the  impure  air. 

The  barium  hydroxide,  which  is  usually  made  up  in 
quantities  of  8  liters  at  a  time,  is  preserved  w4th  especial 
care.  The  hard-glass  bottle  containing  it,  placed  on  a  high 
shelf  so  that  the  measuring  apparatus  can  be  filled  directly 
by  gravity,  is   heavily  coated  on  the  inside  with   barium 

*  J.  Chem.  Soc,  77,  1 1 10  (iqoo). 

t  Woodman  :   /.  Am.  Chem.  Soc,  25,  150  {iQof). 


air:  analytical  methods. 


3S 


carbonate.  The  bottle  is  closed  by  a  rubber  stopper 
with  two  holes,  one  of  which  carries  the  siphon  tube  dip- 
ping to  the  bottom  of  the  bottle  and  supplying  the  meas- 
uring burette,  while  the  other  carries  a  fairly  large  glass  T 
(Fig.  2). 


Fig.  2. 


From  one-half  the  horizontal  arm  of  this  projects  a  glass 
tube  carrying  the  device  for  protecting  the  solution.  This 
device  is  shown  drawn  on  a  somewhat  larger  scale  in  the 
same  sketch.     The  horizontal  tube  enters  the  T  tube  far 


36  AIR,    WATER,    AND    FOOD. 

enough  to  support  the  apparatus.  Connection  is  made 
by  a  closely  fitting  rubber  tube.  The  longer  tube,  reaching 
nearly  to  the  bottom  of  the  test-tube,  carries  a  fairly  good- 
sized  "calcium  chloride  tube"  which  contains  soda-lime, 
enclosed  in  the  usual  manner  by  plugs  of  cotton.  The  test- 
tube  contains  5  to  lo  c.c.  of  dilute  (about  N/50)  caustic 
potash  colored  with  phenolphthalein,  the  whole  ser\4ng  to 
indicate  the  efficiency  of  the  soda-lime.  From  the  other 
end  of  the  horizontal  arm  of  the  T  projects  in  the  same  way 
a  long  tube  bent  at  right  angles  fitting  by  a  rubber  stopper 
into  the  top  of  the  burette,  thus  making  the  whole  a  closed 
system,  much  after  the  manner  of  Blochmann.*  Any  air 
entering  the  bottle  when  the  solution  is  drawn  from  the 
burette  or  when  the  burette  is  filled  again  must  have  come 
through  the  protecting  apparatus.  This  will  be  found 
efficient  if  care  is  taken  in  the  selection  or  preparation  of 
the  soda-lime. t 

The  burette  used  for  the  barium  hydroxide  is  a  glass- 
stoppered  one,  differing  somewhat  from  the  ordinary  form. 
The  lower  portion  below  the  graduations  is  narrowed  and 
bent  at  right  angles.  This  horizontal  part  is  fitted  with  an 
ordinary  glass  stop-cock.  This  gives  no  trouble  when  kept 
well  vaselined.  The  tip  of  the  burette  is  kept  covered  with 
a  little  rubber  cap  when  not  in  use  to  prevent  clogging  from 
the  formation  of  carbonate.  The  apparatus  could  easily  be 
arranged  with  a  special  pipette  for  the  delivery  of  a  definite 
charge  of  baryta  solution  if  desired. 

The  bottles  used  for  the  collection  of  samples  are  of 
hard  glass  of  about  2  liters  capacity,  the  exact  volume  being 
determined  in  each  case  to  a  cubic  centimeter.     The  bottle 


*  Ann.  Chem.  (Liebig),  237,  39  (^<?'^7)- 

t  Directions  for  preparing  a  good  quality  of  soda-lime  are  given  by  Benedict 
and  Tower:   /.  Am.  Chem.  Soc,  21,  396  {i8qq). 


air:  analytical  methods. 


37 


is  dosed  by  a  rubber  stopper  through  which  pass  two  glass 
tubes  about  7  mm.  in  diameter.  The  longer  tube  reaches 
almost  to  the  bottom  of  the  bottle;  the  shorter  tube  ends 
internally  just  flush  with  the  stopper.  Both  tubes  project 
externally  about  two  inches  and  are  provided  with  stop- 


FiG.  3. 


cocks  at  slightly  different  levels  so  as  to  permit  of  convenient 
manipulation.  There  is  permanently  attached  to  the  upper 
end  of  the  longer  tube  a  piece  of  rubber  tubing  i  inch  in 
length  which  serv^es  to  connect  it  with  the  tip  of  the  baryta 
burette.  The  stop-cocks  may  be  replaced  by  rubber  tubing 
and  Mohr  pinch-cocks  if  desired. 


38  AIR,    WATER,    AND    FOOD. 

The  apparatus  used  for  filtering  off  the  barium  carbonate 
is  shown  in  Fig.  3. 

To  the  base  of  a  ring-stand  is  firmly  clamped  an  ordinary 
filter-bottle  of  about  250  c.c.  capacity  closed  by  a  rubber 
stopper  with  two  holes.  Through  one  of  these  passes  a  tube 
leading  to  the  suction-pump,  through  the  other  the  tube  of 
a  Gooch  filtering-funnel,  the  upper  part  cf  which  is  cut  off 
so  that  the  remainder  above  the  constriction  is  about  an 
inch  long.  The  tip  projecting  into  the  bottle  is  bent  so  that 
the  liquid  shall  flow  down  the  side  and  not  spatter.  A 
rather  close  coil  of  stout  platinum  wire  placed  above  the 
narrow  portion  serves  as  a  support  for  the  asbestos  filter, 
or  can  be  removed  if  it  is  desired  to  use  a  cotton  plug  instead. 
In  the  upper  part  of  the  tube  is  tightly  fitted  a  rubber 
stopper  through  which  passes  a  narrow  glass  tube  extending 
to  within  one-eighth  inch  of  the  asbestos  layer  and  provided 
above  the  stopper  with  a  stop-cock.  Connection  is  made 
with  the  short  tube  of  the  inverted  bottle  by  means  of  a 
rubber  tube  about  8  inches  in  length. 

Procedure. — (a)  The  Absorption. — Insert  the  tip  cf  the 
baryta  burette  into  the  short  piece  of  rubber  tubing  and  run 
in  approximately  50  c.c.  with  both  stop-cocks  open.  Close 
the  outlet  cock,  pinch  the  rubber  tube  with  the  fingers, 
detach  it  from  the  burette  and  insert  a  bit  of  glass  rod  to 
keep  out  the  air.  Finally  close  the  stop-cock.  Drain  the 
burette  three  minutes  and  take  the  reading  as  usual. 
Carry  out  the  absorption  of  the  carbon  dioxide  as  described 
in  the  Pettenkofer  method,  except  that  25-30  minutes  is 
ample  for  the  absorption. 

(b)  The  Filtration. — While  the  absorption  is  in  progress 
prepare  the  filter.  Apply  slight  suction  and  add  enough 
asbestos  fiber  suspended  in  water  to  form  a  felt  about  a 
sixteenth  of  an  inch  thick  over  the  platinum  coil.     Wash  it 


air:  analytical  methods.  39 

once  or  twice  with  distilled  water.  If  properly  done  the 
water  should  flow  from  the  filter-tube  in  a  continuous 
stream  when  the  pump  is  running  at  good  speed,  but  should 
drop  only  slowly  when  the  suction  is  slight. 

Prepare  also  about  100  c.c.  of  "wash- water"  by  adding^ 
to  distilled  water  i  c.c.  of  a  10  per  cent,  barium  chloride 
solution  and  three  drops  of  phenolphthalein,  then  titrating 
with  the  barium  hydroxide  to  a  faint  permanent  pink.  Keep 
in  a  stoppered  flask  until  wanted. 

Measure  into  the  filter-bottle  25  c.c.  of  the  hydrochloric 
acid. 

The  arrangement  of  the  bottle  and  filter  during  filtration 
is  shown  in  the  figure. 

Open  the  stop-cock  of  the  shorter  tube  and  turn  on  the 
pump.  Now  slowly  open  the  filter  stop-cock  and  control  the 
flow  of  liquid  entirely  with  this  cock.  The  barium  carbonate 
remains  on  the  asbestos,  and  the  clear  baryta  solution  which 
passes  through  is  at  once  neutralized  by  the  hydrochloric 
acid.  When  all  the  liquid  has  passed  through  allow  the 
pump  to  act  for  a  few  minutes  to  partially  exhaust  the 
bottle,   then  close  the  filter-cock. 

Pour  some  of  the  wash-water  into  a  small  beaker,  dip 
the  end  of  the  longer  tube  into  it,  and  by  opening  the  stop- 
cock allow  about  20  c.c.  to  flow  into  the  bottle  before  again 
closing  it.  Unclamp  the  bottle  and  shake  thoroughly  while 
held  horizontally  and  still  attached  to  the  filter.  Clamp  it 
in  place  again,  turn  on  the  pump,  and  drain  oft'  the  wash- 
water.  Repeat  this  twice.  Generally  at  the  third  washing 
the  wash-water  is  no  longer  turned  pink,  showing  that  the 
barium  hydroxide  has  been  completely  removed.  Remove 
the  stopper  and  cock  from  the  filter-tube  and  draw  the  re- 
mainder of  the  wash-water  through  the  filter  to  wash  down 
the  sides  of  the  tube. 


40  AIR,    WATER,    AND    P^OOD. 

(<;)  The  Titration. — Transfer  the  acid  solution  to  a  6-inch 
porcelain  dish  and  run  in  barium  hydroxide  to  the  produc- 
tion of  a  distinct  pink  color.  Return  the  solution  to  the 
filter-bottle  and  pour  it  again  into  the  dish.  One  or  two 
drops  of  the  alkali  solution  will  suffice  to  finish  the  titra- 
tion. 

Note. — It  will  be  seen  that  in  this  method  the  errors  of 
the  other  are  largely  avoided.  The  alkali  solution  is  made 
weaker,  and  its  time  of  contact  with  the  glass  of  the  bottle 
is  shorter;  the  barium  carbonate  is  entirely  removed  if  the 
-filtration  is  properly  conducted ;  the  titration  is  not  carried 
out  in  an  alkaline  solution,  but  in  one  that  is  acid. 

For  a  discussion  of  the  results  obtained  the  papers  cited 
above  may  be  consulted. 

Strong  potassium  hydroxide  is  undoubtedly  the  best  absorb- 
ent for  carbon  dioxide  and  in  all  cases  where  delicate  manipula- 
tion and  expensive  apparatus  are  not  hindrances,  some  form 
of  gas  absorption  apparatus  is  best.  The  measurement  of  the 
gas  should  be  made  over  mercury  and  in  a  finely  calibrated 
tube.  Eimer  and  Amend  now  supply  a  modification  of 
the  Petterson  and  Palmquist  apparatus  which  gives  good 
results. 

General  Tests. — In  addition  to  the  above  methods  for 
determining  carbon  dioxide  just  described,  there  are  general 
tests  which  can  often  be  used  with  advantage.  If  within  the 
space  of  a  few  hours  some  fifty  or  more  tests  are  to  be  made,  and 
comparative  results  rather  than  great  accuracy  are  required, 
some  simpler  form  of  apparatus  is  desirable. 

Such  an  apparatus,  to  be  satisfactory,  should  meet,  so 
far  as  possible,  the  following  requirements: 

(i)  It  should  be  sufficiently  compact  and  portable  to  be 
carried  in  the  hand  from  place  to  place. 


air:  analytical  methods.  41 

(2)  It  should  be  as  simple  in  construction  as  possible, 
and  its  use  should  not  involve  delicate  measurements. 

(3)  If  possible,  the  apparatus  should  be  made  entirely 
of  glass,  avoiding  prolonged  contact  of  corks  or  of  rubber 
connectors  with  any  dilute  solution  which  may  be  used. 

(4)  It  should  be  so  constructed  as  to  protect  the  solution 
at  all  times  from  the  carbon  dioxide  of  the  air,  especially 
while  the  determination  is  being  made,  because  of  necessity 
such  an  apparatus  must  be  used  within  the  area  of  contami- 
nation. 

(5)  The  complete  apparatus  should  be  sufficient  for  fifty 
or  more  determinations. 

(6)  It  must  be  capable  of  giving  results  of  a  reasonable 
degree  of  accuracy,  say  wdthin  0.5  part  of  carbon  dioxide  in 
10,000  parts  of  air,  in  the  hands  of  persons  having  little  or 
no  chemical  knowledge  and  minimum  skill  in  manipula- 
tion. 

(7)  If  a  solution  be  used  in  the  apparatus  it  should  be 
one  w^hich  can  be  prepared  easily  from  chemicals  readily 
obtained;  the  solution  must  maintain  its  efficiency  for  a 
reasonable  length  of  time,  if  protected  from  external  influ- 
ences; and  the  solution  should  be  one  that  is  not  at  all 
dangerous  or  obnoxious  to  use. 

Simplicity  of  apparatus  is  much  to  be  desired,  but  it 
should  not  be  gained  at  too  great  sacrifice  of  accuracy.  Even 
when  no  greater  precision  is  required  than  is  necessary  to 
meet  the  demands  of  practical  work,  it  is  out  of  the  question 
to  measure  the  test  solution  by  means  of  an  ordinary  pipette 
or  to  preserve  it  for  any  length  of  time  in  stoppered  vials; 
the  strength  of  the  solution  is  almost  certain  to  be  reduced 
by  contamination  with  the  breath,  by  contact  with  rubber 
or  cork. 


42 


AIR,    WATER,    AND    FOOD. 


It  must  ever  be  borne  in  mind  that  extreme  care  is 
necessary  in  the  preparation  and  use  of  these  very  dilute 
solutions,  the  strict  observance  of  conditions  which  might 
well  be  neglected  in  ordinary  analytical  procedures  being 
here  an  essential  factor  of  success. 

For  the  preservation  and  measuring  of  the  test  solution 
the  authors  have  devised  an  apparatus  which  appears  to 
answer  the  above  requirements,  and  in  actual  practice  has 
been  found  satisfactory.* 

The  essential  feature  of  this  apparatus  consists  of  an 
automatic  pipette  for  measuring  the  test  solution.  This  is 
a  modified  form  of  the  pipette  first  pro- 
posed by  G.  P.  Vanier  and  in  use  in  this 
laboratory  for  a  number  of  years.  A  gen- 
eral idea  of  it  may  be  had  from  Fig.  4- 
The  manner  of  using  it  is  extremely  simple. 
The  test  solution  is  preserved  in  a  i -liter 
bottle  of  hard  glass  provided  with  a  doubly 
perforated  rubber  stopper.  Through  one 
opening  passes  the  siphon  tube  of  the  pi- 
pette, which  is  sufhciently  long  to  reach  to 
the  bottom  of  the  bottle ;  through  the  other 
passes  a  glass  tube  ending  just  below  the 
stopper  and  connected  with  a  small  bottle 
containing  fresh  soda-lime.  By  means  of 
the  three-way  cock  the  solution  is  allowed 
to  flow  into  the  small  inside  pipette  until 
it  overflows.  The  stop-cock  is  then  turned 
and  the  solution  allowed  to  flow  out 
at  the  lowest  point.  The  pipette  is 
made  of  such  a  size  as  to  deliver  exactly 
10  cubic  centimeters.      The    entrance  of  atmospheric  ccir- 

*  Air  Testing  for  Engineers. 
Quar.,   14,  94  {1901)' 


Fig.  4. — Automatic 
Pipette. 


A.  G.  Woodman  and  Ellen  H.  Richa''ds:    Tecli. 


AIR:    ANALYTICAL    METHODS.  43 

bon  dioxide  as  the  solution  flows  out  is  prevented  by  the 
small  tube  containing  soda-Hme  or  bits  of  caustic  potash. 
The  excess  of  liquid  which  accumulates  in  the  over'flow 
reservoir  may  be  drawn  off  when  desired.  The  bottle  and 
■pipette  are  contained  in  a  wooden  case  about  20X8x7  inches, 
outside  dimensions,  and  with  the  solution  weigh  about  8 
pounds.  The  case  is  furnished  with  a  handle  at  the  top  so 
that  it  may  be  carried  readily  in  the  hand  from  place  to 
place.  The  bottle  is  fastened  to  the  case,  and  the  lower 
end  of  the  pipette  is  clamped  to  a  wooden  support  to  keep 
it  from  swinging.  The  stopper  should  be  firmly  fastened 
to  prevent  loosening. 

The  bottle  should  be  thoroughly  cleaned  and  washed 
with  potassium  bichromate  and  sulphuric  acid,  and  it  is 
best  also  to  steam  it  for  half  an  hour  or  so.  As  a  further 
measure  of  precaution  the  rubber  stopper  is  boiled  with 
dilute  caustic  potash  and  thoroughly  washed,  although  the 
solution  can  come  in  contact  with  it  only  through  splashing 
while  the  case  is  being  carried. 

This  measuring  apparatus  may  be  used  with  a  variety  of 
methods  and  with  various  strengths  of  solution. 

The  general  tests  are  based  on  two  fundamental  principles. 
For  instance,  the  Fitz  and  Wolpert  methods  are  carried  out 
by  shaking  a  small  quantity  of  dilute  lime-water,  colored  pink 
by  phenolphthalein,  with  successive  portions  of  air  until  the 
solution  is  decolorized.  The  greater  the  amount  of  carbon 
dioxide  in  the  air  the  less  will  be  the  volume  of  air  required 
to  neutralize  the  lime-water,  and  vice  versa.  That  is,  the  amount 
of  lime-water  remaining  constant,  the  amount  of  carbon 
dioxide  will  vary  in  a  certain  inverse  ratio  to  the  volume  of 
air. 


44  AIR,    WATER,    AND   FOOD. 

The  method  of  Cohen  and  x\ppleyard*  is  based  upon  the 
fact  that  if  a  dilute  solution  of  lime-water,  slightly  colored 
wdth  phenolphthalein,  is  brought  in  contact  with  a  sample 
of  air  containing  more  than  enough  carbon  dioxide  to  com- 
bine with  all  the  lime  present,  the  solution  wall  be  gradually 
decolorized,  the  length  of  time  required  depending  upon 
the  amount  of  carbon  dioxide  present.  That  is,  the  quantity 
of  lime-water  and  the  volume  of  air  remaining  the  same  in 
each  case,  the  rate  of  decolorization  will  vary  inversely  with 
the  amount  of  carbon  dioxide.  The  method  is  scientific  in 
principle  because  it  recognizes  the  fact  that  the  absorption 
of  carbon  dioxide  by  dilute  alkali  solutions  is  a  tinie- 
reaction. 

The  method  of  preparation  of  the  solutions  and  the 
manner  of  making  the  tests  w^hich  have  been  found  to  give 
the  best  results  will  be  described  in  detail,  since  experience 
has  shown  that  these  directions  cannot  be  too  minute. 

Preparation  of  the  Test  Solution. — The  solution  used  is 
a  dilute  solution  of  lime-water  colored  wdth  phenolphthalein. 
To  freshly  slaked  lime  add  twenty  times  its  w^eight  of  water 
in  a  bottle  of  such  size  that  it  is  not  more  than  two-thirds 
full.  Shake  the  mixture  continuously  for  20  minutes,  and 
then  allow  it  to  settle  over  night  or  until  perfectly  clear. 
The  resulting  solution  is  the  stock  lime  solution,  or  "satu- 
rated lime-water."  If  made  in  the  manner  indicated,  each 
cubic  centimeter  of  it  ought  to  be  very  nearly  equivalent 
to  I  milligram  of  carbon  dioxide.  If,  how^ever,  it  is  desired 
to  know  the  strength  of  it  more  exactly,  it  may  be  deter- 
mined by  standard  acid. 

To  prepare  the  "test  solution,"  pour  into  the  i -liter 
bottle  of  the  testing  apparatus  i  measured  Hter  of  distilled 

*  Chem.  News,  70,    {1894),  iii. 


air:  analytical  methods.  45 

water,  and  add  2.5  ex.  of  a  solution  of  phenolphthalein  (made 
by  dissolving  0.7  gram  of  phenolphthalein  in  50  c.c.  of 
alcohol  and  adding  an  equal  volume  of  water).  Stand  the 
bottle  on  a  sheet  of  white  paper  and  add  the  "saturated 
lime-water  "  drop  by  drop  from  a  pipette,  shaking  the  bottle 
thoroughly  after  each  addition  until  a  faint  pink  color  is 
produced  which  is  permanent  for  one  minute.  Now  add 
6.3  c.c.  of  the  "saturated  lime-water,"  shake,  and  imme- 
diately connect  the  bottle  again  to  the  apparatus. 

For  accuracy  in  testing  air  which  is  high  in  carbon  dioxide, 
it  is  found  advantageous  to  use  a  solution  twice  as  strong  as 
the  above.  This  double  solution  is  prepared  in  precisely  the 
same  way,  using  5.0  c.c.  of  the  phenolphthalein  solution  and 
12.6  c.c.  of  the  "  saturated  lime-water." 

While  this  procedure  does  not  give  an  exact  volume  of 
solution,  it  is  believed  to  be  the  best  for  the  preparation 
of  this  dilute  test  solution,  since  it  obviates  the  necessity 
for  pouring  the  prepared  solution  from  the  measuring-flask 
into  the  bottle  in  which  it  is  kept;  12.6  c.c.  of  the  stock 
lime  solution  is  added  rather  than  10  c.c,  in  order  to  keep 
the  values  obtained  with  the  resulting  solution  more  nearly 
comparable  with  the  older  values  calculated  on  the  suppo- 
sition that  10  c.c.  of  **  saturated  hme- water  "  was  equivalent 
to  12.6  milligrams  of  carbon  dioxide. 

Method  of  Making  the  Test. — The  Fitz  shaker  or  appara- 
tus for  measuring  the  volume  of  air  used,  consists  of  a  tube 
of  about  30  cubic  centimeters  capacity,  closed  at  one  end,, 
and  graduated  for  a  distance  of  20  cubic  centimeters  from 
the  closed  end.  In  this  tube,  by  means  af  a  rubber  collar, 
slides  a  smaller  tube  which  is  contracted  at  the  outer  end 
so  as  to  be  more  readily  closed  by  the  finger.  The  appa- 
ratus is  shown  full  size  in  Fig  5. 


46 


AIR,    WATER,    AND    FOOD. 


See  that  the  inner  tube  of  the  shaker  slides  readily  in 
the  outer  one,  moistening  the  rubber  collar  slightly  if 
necessary.     Have    the    inner   tube    pressed    down    to    the 

bottom  of  the  larger  one,  and 
measure  into  the  apparatus  lo 
cubic  centimeters  of  the  test  solu- 
tion from  the  automatic  pipette,  or 
from  a  burette,  as  in  Fig.  2.  Pull 
the  inner  tube  up  to  the  5-c.c.  mark 
(the  bottom  of  the  inner  tube  serv- 
ing as  the  index)  and  close  the  end 
of  the  tube  with  the  finger.  Hold 
the  apparatus  horizontally,  and 
shake  it  vigorously  for  exactly  30 
seconds. 

The  amount  of  air  that  is  thus 
brought  in  contact  with  the  solution 
is  equivalent  to  approximately  30 
cubic  centimeters,  as  there  are  25 
cubic  centimeters  of  air  above  the 
liquid  when  the  small  tube  is  forced 
to  the  bottom  of  the  larger.  Re- 
move the  finger,  press  down  the 
small  tube  again  to  the  bottom  of 
the  larger  and  draw  it  up  to  the 
20-c.c.  mark.  Shake  the  apparatus 
again  for  30  seconds.  The  amount 
of  air  brought  in  contact  with  the 
solution  is  now  30  +  20  =  50  c.c. 
Repeat  the  shaking,  using  20  c.c. 
of  fresh  air  each  time,  until  the 
pink  color  is  discharged.  The  amount  of  carbon  dioxide 
corresponding  to  the  number  of  cubic  centimeters  of  air 
used  will  be  found  in  Table  A. 


10 


Pig.  s.-r-FitzShaker, 
Full  Size.  . 


air:  analytical  methods. 


47 


Acting  on  the  same  principle  is  the  Wolpert  shaker  shown 
in  Fig.  5^.     This  cyhnder  is  easier  to  manipulate  and  results 
obtained  with  it  by  students  are  more 
-consistent  than  those  obtained  with  the 
Fitz. 

TABLE    A. 


Double 

Standard  Test 

Solution. 

Cubic  Centimeters 

Solution. 

CO2  in  10,000. 

of  Air. 

COi  in  10,000. 

22.2 

50 

15-6 

18.0 

70 

12.4 

I5-I 

90 

10.2 

13.0 

IIO 

8-7 

"•3 

130 

7-5 

9.9 

150 

6.6 

8.8 

170 

5-8 

8.0 

190 

5-2 

7-3 

210 

4.8 

6.8 

230 

4-5 

6.3 

250 

4-3 

5-9 

270 

4.1 

5-6 

290 

3-95 

5-4 

310 

3-8 

5-1 

330 

H 

4.8 

350 

3.6 

4-7 

370 

4-5 

390 

4.4 

410 

4.2 

450 

4.0 

490 

3-9 

530 

The  following  notes  and  precautions 
apply  to  both  forms  of  the  shaker. 
Care  should  be  taken  that  the  finger 
used  to  close  the  end  of  the  tube  is 
perfectly  clean,   since   on   a  warm  day  ig.  5a. 

the  free  acid  in  the  perspiration  might  easily  vitiate  the 
results.  Some  may  find  the  use  of  a  rubber  stopper  prefer- 
able. 

If  greater  accuracy  is  desired,  the  shaker  should  be  filled 
with  the  air  to  be  tested  before  running  in  the  test  solution. 


48  AIR,   WATER,    AND    FOOD. 

This  may  be  done  readily  by  filling  the  shaker  with  water 
and  emptying  it. 

The  apparatus  should  be  shaken  vigorously  and  contin- 
uously during  the  30  seconds  in  order  to  absorb  practically 
all  of  the  carbon  dioxide  in  the  enclosed  air.  The  number 
of  shakings  ought  not  to  be  less  than  100  during  this  time. 

Care  should  be  taken  not  to  contaminate  the  air  while 
the  sample  is  being  taken.  The  breath  should  be  held  momen- 
tarily while  the  air  in  the  apparatus  is  being  replaced,  and  the 
sample  should  be  collected  as  far  to  one  side  of  the  body  as 
possible.  It  ought  not  to  require  over  10  seconds  to  replace 
the  air,  and  the  entire  test,  with  air  containing,  say,  8  parts 
of  carbon  dioxide  per  10,000,  should  not  require  over  6 
minutes. 

If  less  than  90  c.c.  of  air  is  required  to  discharge  the  pink 
color,  the  test  should  be  repeated,  using  10  c.c.  of  air  each 
time  after  the  first  30  c.c. 

It  is  not  necessary  to  rinse  out  the  shaker  after  making 
each  test,  but  it  should  be  carefully  washed  and  dried  after 
using,  and  the  parts  kept  separate  when  not  in  use. 

The  "  double  solution  "  is  used  in  exactly  the  same  manner 
and  amount  as  the  regular  test  solution,  reference  being  made 
to  the  appropriate  portion  of  the  table. 

For  the  Cohen  method  the  same  solutions  may  be  used 
and  measured  from  the  same  apparatus.  The  samples  are 
collected  in  white,  glass-stoppered  bottles  of  one-half  liter 
capacity.  This  may  be  done  by  aspirating  the  air  with  a  bel- 
lows, or  the  bottles  may  be  completely  filled  with  water,  which 
is  then  emptied  at  the  place  where  the  air  is  to  be  tested. 

A  convenient  modification  of  this  is  the  water  siphon  method. — 
Two  bottles  (diameter  one-third  the  height)  of  nearly  equal 
capacity  are  iittf^d  with  rubber  stoppers  carrying  small  glass 
tubing,  connected  by  several    feet  of  rubber  connector  with 


air:  analytical  methods. 


49 


clamps   (Fig.  6).     One  bottle  is  completely  filled  with  water, 
nearly  free  from  carbon  dioxide. 

The  pair  of  bottles  is  taken  to  the  place  from  which  the  air 
is  to  be  collected.     The  inlet  tube  may  be  long  to  reach  to  near 


\J^ 


Fig.  6. 


the  ceiling,  or  short;  if  long,  the  first  siphoning  should  be 
rejected,  to  secure  filling  the  inlet  tube  with  the  air  desired, 
the  stoppers  exchanged,  and  the  sample  taken.  The  air-filled 
bottle  is  stoppered  and  taken  to  the  laboratory;  or  the  test 
solution  is  at  once  added,  the  bottle  stoppered  and  shaken, 
noting  minutes  and  seconds.     One  bottle  of  water  with  a  small 


AIR,   WATER,    AND   FOOD. 

reserve  wiU  serve  for  a  number  of  takings  before  absorbing  a 
deleterious  amount  of  CO2.     (See  Fig.  6.) 

A  method  mvolvmg  more  preparation  but  less  troubk  m 
the  field  is  the  steam  .acuum  meth.i.  The  ^^-m  is  s^W  -d 
bv  a  500  ex.  flask  serving  as  a  boiler   xvith  a  Tirnll  burner  to 


pi(,     7. _Steam- Vacuum  Apparatus. 
From  the  thesis  of  Carl  E.  Hanson.  1908. 

supply  the  heat.  The  flask  (Fig.  7)  -  fitted  with  a  rubber 
Zper  carrying  a  No.  6  glass  tube  bent  so  that  one  end  extends 
wi  one  half-inch  of  the  bottom  of  «- ^^^^^^en  placed  in 
position  on  the  stand.  The  bottles  used  ^  "^^b-^;  ^'^^ 
capacity,  made  for  a  ground-glass  stopper  but  fitted  with  a 
rubber  stopper. 


air:   analytical  methods. 


51 


To  prepare  the  jet,  the  water  in  the  flask  is  allowed  to  boil 
ior  five  minutes  in  order  to  expel  completely  the  air  in  the 
water  and  the  flask.  The  pressure  should  be  sufficient  to  throw 
the  vaporized  steam  at  least  one  foot  above  the  exposed  end 
of  the  tube. 

The  empty  bottle  is  placed  on  the  stand  in  an  inverted 
position  and  allowed  to  remain  for  three  minutes.  In  the  mean- 
time a  thin  coating  of  vaseline  is  applied  half  way  up  the  sides 
of  the  stopper.  The  vaseline  acts  as  an  unguent,  reducing 
the  coefficient  of  friction  to  such  an  extent  that  the  principal 
resistance  is  due  to  the  reaction  of  the  stopper  against  com- 
pression. This  enables  one  to  force  the  stepper  in  far  enough 
to  bring  the  glass  and  rubber  into  intimate  contact,  which  is 
essential.  The  vaseline  also  fills  the  interstices  between  the 
rubber  and  the  glass,  which  makes  leakage  impossible. 

Protecting  the  hand  with  a  cloth,  the  bottle  is  raised  from 
the  stand,  and  the  instant  it  clears  the  end  of  the  tube  the 
stopper  is  inserted  while  the  bottle  is  still  inverted.  The 
stopper  may  be  pushed  in  more  securely  by  pushing  it  against 
the  table  with  a  few  pounds  pressure  while  the  bottle  is  still 
in  the  inverted  position.  The  stopper  is  kept  in  under  this 
pressure  for  a  few  minutes  until  the  vacuum  begins  to  form, 
after  which  the  atmospheric  pressure  will  keep  it  in  place. 

All  the  bottles  required  are  treated  in  the  same  way.  The 
rubber  stoppers  should  be  at  least  one  size  larger  than  would 
ordinarily  be  used  for  the  bottles,  and  should  project  three- 
eighths  of  an  inch  or  more  to  be  easily  removed  when  the  sample 
is  to  be  taken. 

Sample  bottles  may  be  tested  for  completeness  of  vacuum 
by  holding  them  in  an  inverted  position  under  water  at  70^ 
F.,  free  from  carbon  dioxide,  and  removing  the  stopper.  After 
the  water  has  replaced  the  vacuum,  the  stopper  is  inserted  and 
the  bottle  removed. 


52 


AIR,   WATER,     AND    FOOD. 


In  making  the  test  lo  ex.  of  the  test  solution  are  run  in 
from  the  automatic  pipette,  or  from  a  burette  as  in  Fig.  2, 
the  time  noted,  and  the  bottle  shaken  continuously  and 
vigorously  with  both  hands  until  the  pink  color  vanishes. 
From  the  time  required  the  amount  of  carbon  dioxide  in  the 
air  may  be  found  by   referring  to  Table  B. 

TABLE    B. 


Double  Solution. 

Time, 
Minutes  and 

"Test  Solution." 

Double  Solution. 

Time. 
Minutes  and 

CO2  in  10,000. 

Seconds 

CO2  in  10,000. 

CO2  in  10,000. 

Seconds. 

0.15 

4.0 

5-45 



0.30 

15-6 

6.00 

.... 

0.45 

12. 1 

3-9 

6.15 

16.0 

1. 00 

9.9 

6.30 

I3-I 

I-I5 

8.4 

3-8 

6.45 

11.4 

1.30 

7.2 

7.00 

lO.I 

1-45 

6.3 

7-15 

9.1 

2.00 

5-5 

3-7 

7-30 

8-3 

2.15 

4.9 

7.6 

2.30 

4.4 

7.0 

2.45 

4.0 

6.5 

3.00 

3-8 

6.1 

3-15 

3-7 

5-7 

3-30 

3-6 

5-4 

3-45 

5-1 

4.00 

4.9 

4-15 

4.7 

4-30 

4-5 

4.45 

4-3 

5.00 

4.2 

5-15 

4.1 

5-30 

Carbon  Monoxide. — The  detection  and  estimation  of 
carbon  monoxide  in  the  very  minute  quantities  in  w^hich 
it  is  found  in  the  air  of  ordinary  rooms  is  a  problem  of 
considerable  difihculty. 

Detection. — Probably  the  most  convenient  test  for  detect- 
ing small  quantities  is  the  blood  test.  Dilute  a  large  drop 
of  human  blood,  freshly  drawn  by  pricking  the  finger,  to  10 
c.c.  with  water.  Divide  the  solution  into  two  equal  portions, 
and  shake  one  portion  gently  for  ten  minutes  in  a  bottle 
containing  about  100  c.c.  of  the  air  to  be  tested.  Compare 
the  tints  of  the  two  portions  by  holding  them  against  a  well- 


air:   analytical  methods.  53 

lio^hted  white  surface.  The  presence  of  carbon  monoxide  is 
indicated  by  the  appearance  of  a  pink  tint  in  the  blood  which 
has  been  shaken  with  air.  One  part  in  10,000  can  be  de- 
tected in  this  way.*  The  dehcacy  of  the  test  can  be  increased 
by  examining  the  bk:)od,  after  shaking  with  the  air,  with 
a  spectroscope.  By  collecting  the  sample  in  an  8-liter  bottle 
and  examining  it  in  this  way  o.oi  part  m  10,000  may  be  detected. 
Determination.f  —  Fr/;/r//'/f.  —  Oxidation  of  the  carbon 
monoxide  to  carbon  dioxide  by  iodine  pentoxide,  iodine 
being  liberated  according  to  the  following  equation: 

IA>+  5  CO  =  I0+  5CO2. 

N 

The  iodine  is  titrated  with sodium  thiosulphate. 

1000  ^ 

Directions. — Place  25  grams  of  iodine  pentoxide,  free  from 

iodine,  in  a  small  U  tube  which  is  suspended  in  an  oil-bath 

and  connected  with  a  small  absorption-bulb  containing  0.5 

gram  of  potassium  iodide  dissolved  in  5  c.c.  of  water.     Heat 

the  oil-bath  to  150°  C,  and  pass  the  air,  previously  drawn 

through   U  tubes, — one   containing  sulphuric  acid   and   the 

other  solid  potassium  hydroxide, — through  the  apparatus  at 

the  rate  of  a  liter  in  two  hours.     Titrate  the  liberated  iodine 

N 

by sodium  thiosulphate  and  starch. 

^  1000  ^ 

Notes. — The  temperature  and  barometric  pressure  should 
be  noted  and  all  volumes  reduced  to  0°  C.  and  760  mm.  pressure. 

Using  1000  c.c.  of  air,  it  is  possible  to  determine  in  this 
Avay  0.25  part  per  10,000,  by  volume,  of  carbon  monoxide. 

The  use  of  tubes  containing  sulphuric  acid  and  potassium 
hydroxide  is  to  free  the  air  from  unsaturated  hydrocarbons, 
hydrogen  sulphide,  sulphur  dioxide,  and  similar  reducing  gases. 

*  Clowes:    "  Detection   and    Estimation  of    Inflammable    Gas   and   Vapor  in 
Ihe  Air,"  p.  138. 

t  Kinnicutt  and  Sanford:   Jour.  Am.  Chem.  Soc,  22  {igoo),  14 


54  AIR,   WATER,    AND    FOOD. 

Nitrites. — The  determination  of  the  amount  of  nitrites 

or  nitrous  acid  in  the  air  can  be  readily  made  as  fo'lows: 

Collect  a  sample  of  the  air  in  a  calibrated  ei"-ht-liter  bottle, 

as  in  the  determination  of  carbon  dioxide.     Add  lOO  c.c.  of 

N 
approximately  —  sodium  hydroxide  solution.     (This  should 

be  free  from  nitrites  and  is  best  made  by  dissolving  metallic 
sodium  in  redis'i  led  water.)  Shake  the  bottle  occasionally 
and  let  it  stand  for  about  twenty-four  hours.  Take  out  50 
c.c.  of  the  solution  and  determine  the  amount  of  nitrites  as 
directed  on  page  108. 

Micro-orgar.isms. — For  the  quantitative  determination 
of  the  number  and  distribution  of  the  micro-organisms  in  air, 
the  method  employed  by  Tucker  ^  in  the  examination  of  the 
air  of  the  Boston  City  Hospital  answers  very  well.  The 
apparatus  used  consists  essentially  of  three  parts:  (i)  a 
special  glass  tube  called  the  aerobioscopc,  in  which  is  placed 
the  filtering  material;  (2)  a  stout  copper  cylinder  of  about 
sixteen  liters  capacity,  fitted  with  a  vacuum-gauge;  (3)  an 
air-pump.  The  filtering  medium  which  is  used  to  retain  the^ 
micro-organisms  is  a  narrow  column  of  sterilized  granulated 
sugar  about  four  inches  long. 

In  using  the  apparatus,  the  required  amount  of  air  is  first 
drawn  from  the  cylinder  by  means  of  the  air-pump.  A 
sterilized  acrobioscopc  is  then  attached  to  the  cylinder  and  the 
air  is  slowly  drawn  through  it,  leaving  its  germs  in  the  sugar- 
filter.  x\fter  the  air  has  l^ieen  drawn  through,  the  aerobioscopc 
is  taken  to  the  culture-room  and  tlie  sugar  dissolved  in 
melted  sterilized  nutrient  gelatine.  The  gelatine  is  con- 
gealed in  an  even  film  on  the  inside  of  the  tube,  where,  after 

*  Report  State  Board  of  Health,  Mass.,  1889,  161. 


air:  analytical  methods.  55 

four  or  five  days,  the  colonies  will  develop,  and  can  be 
counted  bv  the  aid  of  squares  engraved  upon  the  glass. 

This  method  possesses  several  peculiar  advantages.  The 
use  of  a  vacuous  cylinder  allows  a  known  volume  of  air  to  be 
readily  aspirated,  and  the  rate  of  flow  through  the  fiher  is 
easily  controlled.  Another  great  advantage  is  the  use  of  a 
soluble  filter  (sterilized  granulated  sugar),  since  insoluble 
substances  seriously  interfere  with  the  counting.  Further- 
more, the  removal  or  transference  of  the  filter  and  its  germs 
is  avoided.  The  apparatus  is  portable,  and  the  method,  as 
compared  with  others,  is  exceedingly  rapid  of  execution. 

Organic  Matter. — In  regard  to  the  presence  of  organic 
matter  in  the  air  there  is  at  present  considerable  variance  of 
opinion.  While  some  investigators  have  obtained  results 
which  indicate  the  presence  of  such  organic  matter,  it  has 
been  found  also  that  the  amount  which  is  obtained  is  very 
much  less  when  the  dust  of  the  air  is  first  removed  by  filtra- 
tion. The  quantity  of  organic  matter  is  therefore  closely  re- 
lated to  the  amount  of  dust,  and  there  is  strong  evidence  that 
this  dust  in  the  air  is  the  source  of  the  greater  part,  if  not  all, 
of  the  organic  matter,  unless  there  are  present  persons  with 
decayed  teeth,  diseased  lungs,  etc. 

The  methods  of  determination  that  are  in  general  use 
may  be  divided  into  two  groups.  In  the  first  group  are 
those  methods  in  which  the  organic  matter  is  converted  into 
ammonia  and  determined  by  Nessler's  reagent.  In  the  sec- 
ond group  the  organic  matter  is  oxidized  by  boiling  with 
dilute  potassium  permanganate,  the  excess  being  titrated 
with  oxalic  acid.  No  one  method  gives  results  which  are 
wholly  satisfactory,  the  chief  difficulties  being  to  secure  an 
absorbing  material  which  shall  itself  be  free  from  organic 
matter,  and  to  avoid  the  introduction  of  minute  particles  of 
organic  matter  or  dust  during  the  analytical  process. 


56 

Remsen  *  and  Bergey  f  recommend  the  use  of  freshly 
ig-nited  granular  pumice-stone  contained  in  a  narrow  glass 
absorption-tube.  After  aspirating  a  known  volume  of  air, 
the  pumice-stone  is  transferred  to  a  flask,  the  ammonia  dis- 
tilled off  from  alkaline  permanganate  and  estimated  by  Ness- 
ler's  reagent.  Experience  with  the  method  in  this  labora- 
tory has  shown  that  it  is  practically  impossible  to  prepare  the 
pumice-stone  so  that  it  shall  be  absolutely  free  from  organic 
matter,  and  that  the  mere  act  of  transference  of  the  absorb- 
ing material  resulted  in  a  considerable  error.  Miss  Talbot  :J: 
found,  furthermore,  that  all  of  the  organic  matter  is  not  con- 
verted into  ammonia  by  a  single  distillation,  but  that  a  second 
and  third  redistillation  of  the  distillates  uniformly  gave 
higher  results.  She  found  it  preferable  to  draw  the  air 
directly  through  the  boiling  permanganate,  having  the  ap- 
paratus so  arranged  that  the  condensed  steam  was  returned 
to  the  flask.  In  this  way  the  particles  of  organic  matter  were 
returned  again  and  again  to  be  acted  upon  by  the  perman- 
ganate. 

Experience  Avith  all  these  methods  is  well  summed  up  by 
Professor  Remsen  when  he  says:  *'  It  would  be  useless  to 
have  examinations  of  air  made  by  any  but  the  most  careful 
workers.  It  would  be  time  thrown  away  to  have  such  an- 
alyses made  by  the  average  practical  chemist." 

Dust  and  Soot. — The  dust  in  the  air  may  be  estimated  by 
drawing  a  measured  volume  through  tubes  packed  with  cot- 
ton and  noting  the  increase  in  weight.  Soot  may  be  deter- 
mined by  drawing  the  air  through  combustion-tubing  partly 
filled  with  ignited  asbestos,  and  then  determining  the  carbon 
l3y  the  ordinary  methods  of  combustion. 

*  National  Bd.  Health  Bulletin,  I,  233;    II,  517. 

t  Mis.  Coll.  of  Smithsonian  Institution,  No.  1037  {i8g6). 

X  Tech.  Quart.  ^  i  {18S7),  29. 


CHAPTER  V. 

WATER  :    ITS    SOURCE,    PROPERTIES,    AND    RELATION    TO    LIFE 

AND    HEALTH. 

{From  the  Hotisf holder' s  Standpoint.) 

The  metabolism  which  produces  human  energy  is  depen- 
dent upon  the  presence  of  water  in  the  tissues.  This  water 
is  derived  in  part  from  food  which,  as  eaten^  contains  from 
30  to  95  per  cent.;  in  part  from  boiled  water,  as  in  tea  and 
coffee;  or  raw  from  well  or  city  tap.  The  total  daily  supply 
per  person  for  this  purpose  from  all  sources  is  live  or  six 
pints. 

\\'ater  is  also  necessary  to  all  forms  of  vegetable  and 
animal  life,  even  the  lowest  tyj>es,  including  those  inim'cal 
to  human  health.  ^lan  has  always  used  water  as  his  beast  of 
burden:  to  carry  ships  to  the  ocean,  to  turn  mill-wheels,  to 
generate  electrical  power.  He  has  also  forced  it  to  be  his 
scavenger,  carrying  the  refuse  of  his  activities  out  of  his  sight. 
Unless  compelled  by  legal  restrictions,  he  has  given  little 
thought  to  the  effect  on  his  neighbor  of  this  treatment  of 
their  common  property. 

In  common  law,  water  is  held  to  be  a  gift  of  nature  to 
man  for  use  by  all,  and  therefore  not  to  be  diverted  from  its 
natural  channels  for  the  plec.sure  or  profit  of  any  one  to  the 
exclusion  of  the  rest.  Neither  has  one  the  right  to  return 
to  the  channel  water  unfit  for  the  use  of  his  neighbor  farther 
down  the  stream.     That  is,  there  is  no  private  ownership  in 


^y  AIR,    WATER,    AND    FOOD. 

surface-waters  flowing  in  natural  channels.  But  this  inter- 
pretation of  eminent  jurists  has  not  always  been  strictly  fol- 
lowed. Many  cases  have  been  decided,  especially  since  the 
rapid  growth  of  large  cities,  in  direct  contradiction  to  this 
law.  As  population  increases,  cities  need  to  go  farther  and 
farther  into  the  country  for  their  water-supply,  and  they 
often  take  from  the  few  settlers  found  there  the  right  to  the 
water  which  passes  their  doors,  for  the  benefit  of  far-away 
thousands. 

The  law  in  regard  to  that  portion  which  never  enters,  or 
which  escapes  from  visible  channels,  is  less  clear.  It  is  usu- 
ally held  that  this  water  goes  with  the  soil,  and  that  rights 
to  it  may  be  bought  and  sold:  that  wells  may  be  driven  and 
drains  dug,  even  if  a  neighbor's  supply  is  cut  off;  but  it  is 
always  maintained  that  no  man  has  a  right  to  place  any  sub- 
stances on  or  in  the  ground  which  shall  render  his  neighbor's 
well  unfit  for  use. 

The  changes  in  conditions  of  life  have  rendered  impera 
tive  a  careful  study  of  the  ways  and  means  of  practically  com- 
plying with  the  law's  demand  without  a  serious  restraint  upon 
the  progress  of  civilization. 

The  daily  quantity  required  for  each  person  has  increased 
from  the  two  to  four  gallons  drawn  by  bucket  from  the  farm- 
house well  to  thirty  or  forty  gallons  taken  from  the  town  sup- 
ply by  the  turning  of  a  faucet,  and  in  cities  where  much  is  used 
for  manufacturing  purposes,  for  running  elevators  and 
motors,  the  daily  amount  may  reach  lOO  gallons  per  inhabi- 
tant. This  constantly  Increasing  use  of  water  for  other  than 
cleansing  purposes  has  enormously  increased  the  difficulty 
of  securing  clean  water  for  domestic  use.  Not  only  is  a 
larger  quantity  of  polluting  material  deposited  in  the  water, 
but  it  is  carried  farther  from  its  source  by  the  dilution. 
This  fact,  as  well  as  the  demand  for  higher  standards  of 


water:  source,  properties,  and  relation  to  life.  59 

purity,  has  made  the  abandonment  of  private  water-suppHes 
a  necessity,  and  has  demanded  from  municipahties  the  best 
scientific  knowledge  and  the  most  careful  supervision  of  the 
quality  of  the  public  supply. 

A  city  or  tov^n  is  under  as  strict  obligation  to  furnish  a 
safe  supply  of  water  as  it  is  to  provide  safe  roads.  To  this 
end,  the  proper  construction  and  maintenance  of  reservoirs 
and  a  sufficient  police  surveillance  of  the  watershed  is  as  im- 
portant as  abundance  of  supply. 

Education  of  the  people  at  large  is  still  necessary,  not 
only  that  those  who  depend  in  whole  or  in  part  upon  springs 
and  wells  may  know  how  to  protect  themselves,  but  also  that 
the  necessary  cost  of  the  larger  pubHc  (municipal)  supply 
may  be  cheerfully  paid  for  by  the  citizens. 

Leaving  out  of  the  present  discussion  such  considerations 
as  belong  only  to  the  engineer  and  specialist,  the  problem  of 
potable  water  will  be  treated  in  this  chapter  from  the  point 
of  view  of  the  intelligent  citizen  and  educated  individual  who 
cannot  afTord  to  remain  ignorant  of  so  important  a  factor  in 
the  general  welfare.  The  reason  why  this  education  is  needed 
lies  in  the  fact  that  primitive  habits  of  thought,  influencing 
action  in  every-day  life,  survive  long  after  the  race  has  passed 
beyond  the  original  conditions.  In  no  respect  is  this  more 
true  than  in  regard  to  water. 

The  ideal  drinking-water  of  most  persons  is  the  c^ear^ 
colorless,  sparkling  water  of  a  spring,  refreshing  in  its  cool- 
ness and  satisfying  the  aesthetic  sense  by  its  suggestion  of 
purity.  So  strong  a  hold  has  this  ideal  that  it  is  most  diffi- 
cult to  convince  the  average  person  that  any  water  which  has 
these  characteristics  can  be  other  than  wholesome  and,  con- 
versely, that  water  lacking  in  any  of  these  qualities  is  suitable 
1      for  human  consumption.     Early  man  drank  clear  cool  water 


6o  AIR,    WATER,    AND    FOOD. 

wherever  he  found  it.  If  there  was  not  a  spring  at  hand,  he 
scooped  out  a  hole  in  the  sand.  Pioneer  settlers  dug  the 
well  as  near  the  kitchen  door  or  the  barnyard  as  they  could 
find  water,  with  a  blind  faith  in  the  protecting  power  of 
mother  earth,  not  wholly  misplaced  so  long  as  the  require- 
ments of  the  household  did  not  exceed  two  or  three  gallons 
per  person  daily,  and  so  long  as  the  nearest  neighbor  was 
half  a  mile  away.  So  persistent  is  this  confidence  in  nature 
that  in  the  light  of  this  day  a  majority  of  intelligent  people, 
even,  will  quaff  at  a  roadside  well  or  drink  freely  at  a  country 
hotel  or  go  to  live  in  a  city  without  ever  taking  thought  for 
the  quality  of  the  water.  Water  is  water,  and  he  who  pauses 
with  his  glass  half-way  and  asks  whence  comes  the  supply  is 
scouted  as  a  weak-minded  crank.  So,  too,  when  town  au- 
thorities have  spared  no  pains  or  expense  to  secure  a  safe 
supply  from  a  distant  lake,  and  have  guarded  it  by  all  means 
known  to  science,  the  primitive  habit  of  thought  requiring 
colorless  water  of  an  even  coolness  of  temperature  leads 
those  who  can  afford  it  to  purchase  "  spring  "-wa'er  in  jugs 
and  bottles,  with  the  blind  faith  of  the  savage  tha,  what  comes 
out  of  the  ground  must  be  good. 

Fundamental  race-habits  are  taken  advantage  of  by  the 
dealer  in  spring-waters  as  well  as  by  the  vendor  of  patent 
medicines — the  missionary  has  no  chance  against  him. 
From  the  schools  and  colleges  there  should,  however, 
be  sent  out  a  generation  of  more  intelligent  persons  who, 
learning  to  weigh  evidence,  will  not  take  chances  and 
will  help  to  develop  a  public  opinion  on  sanitary  matters, 
especially  in  regard  to  water-supplies.  For  not  until 
there  is  an  intelligent  pubHc  can  the  present  reckless  use  of 
water  and  ground  be  stopped.  While  no^  everv  man  may 
be  a  chemist,  he  can  have  that  modicum  of  knowledge  which 
will  enable  him  to  understand  the  need  of  chemical  tests  of 


water:  source,  properties,  and  relation  to  life.  6i 

water  and  to  distinguish  between  the  work  of  the  expert  and 
the  amateur. 

However  safe  this  ideal  of  clear,  colorless  water  may  have 
been  in  early  times,  it  must  now  be  relegated,  with  the  un- 
barred door  and  unwatched  treasure,  to  the  mountain  fast- 
nesses. As  the  country  becomes  settled,  appearance  and 
taste  are  no  longer  sufficient  guides;  therefore  scientific  tests 
must  be  applied  and  the  results  interpreted  by  trained  ob- 
servers to  whom  the  individual  subordinates  his  private 
judgment. 

The  ideal  water  should  be  above  suspicion,  for  if  it  has 
once  been  contaminated,  who  can  tell  how  soon  it  will  find 
bad  company  again?  Not  the  analyst  in  his  laboratory.  In 
fact,  the  laboratory  verdict  is  worth  very  little  without  a 
knowledge  of  outside  conditions  and  without  a  keen  detec- 
tive insight  W'hich  scents  out  the  most  unlikely  causes. 
Nevertheless  the  evidence  given  by  analytical  results  is 
needed  to  procure  conviction. 

Although  "  pure  "  water  is  found  only  in  the  laboratory, 
"  safe  "  water,  that  which  is  reasonably  free  from  objection- 
able substances,  mineral  and  organic,  may  be  obtained  w^th 
sufficient  care  and  knowledge. 

A  clear  understanding  of  the  problem  requires  a  clpse 
study  of  the  circulation  of  water  on  the  earth.  Let  us  trace 
the  course  of  water  from  sky  to  ocean,  in  view  of  its  availa- 
bility for  domestic  use,  and  note  the  dangerous  properties  it 
may  acquire,  considering  also  the  changes  in  condition  which 
it  may  undergo  in  its  course  from  mountain  to  sea. 

Water-vapor  rising  from  sea  and  land  is  condensed  in  the 
upper  air,  then  falls  to  the  earth,  absorbing,  as  it  does  so, 
ammonia,  carbon  dioxide,  sulphur  oxides,  and  other  soluble 
gases,  if  present,  and  washing  the  air  free  from  dust-particles, 
mineral  and  organic. 


62  AIR.    WATER,    AND    FOOD. 

This  meteoric  water  (rain  or  snow),  although  nearly  free 
from  dissolved  mineral  substances,  is  therefore  by  no  means 
pure.  Furthermore,  rain  falling  on  insoluble  rocks,  bare  or 
lichen-covered,  or  on  loose,  sandy  soils,  washes  them  also, 
giving  up  to  the  vegetation  the  ammonia  and  taking  in  re- 
turn carbon  dioxide  and  dissolved  albuminoid  ammonia. 

\Vater  thus  enriched  has  increased  solvent  power  on  cer- 
tain rocks  and  soils.  This  rain-water  soon  forms  rivulets 
which,  passing  down  from  the  highlands  into  the  forest,  spread 
over  the  moss-covered  area,  soaking  the  leaves  and  peaty  soil 
and  extracting  organic  substances.  Mountain  brooks,  as  well 
as  lowland  streams,  draining  a  region  free  from  limestone,  are 
thus  colored  brownish-yellow  and  furnish  "  meadow-tea,"  as 
Thoreau  happily  named  it.  As  the  stream  flows  on  it  re- 
ceives contributions  of  many  kinds — the  overflow  of  springs, 
the  under-drainage  from  cultivated  fields,  the  surface-wash 
from  pasture  and  meadow.  Scavengers  are,  however,  con- 
stantly at  work.  Brought  as  dust  by  the  ever-passing  air- 
currents,  seeds  of  tiny  plants  freely  sprout  in  the  water  and 
grow  rapidly  whenever  a  quiet  pool  or  lake  gives  oppor- 
tunity. The  products  of  organic  decay  and  the  ammonia  of 
the  rain  may  be  thus  removed  and  the  water  pass  on  to  the 
reservoir  clear  and  soft  and  as  nearly  pure  as  nature  furnishes. 
It  is,  however,  becoming  rare  to  find  even  a  mountain  stream 
or  forest  brook  which  has  not  been  subjected  to  modification 
by  human  agencies.  Three  kinds  of  contamination  may  take 
place.  First:  A  farmhouse  high  up  on  the  hillside  lays  trib- 
ute for  drinking  purposes  upon  that  water  finding  its  way 
beneath  the  sand  which  appears  in  the  form  of  a  spring.  The 
overflow  is  made  into  a  duck-pond,  or  passes  through  the 
watering-trough  by  the  roadside  before  it  joins  other  water 
tumbling  over  the  rocks  as  a  rapid  stream.  The  brook  thus 
grown  larger  widens  out  a  little  below  the  farmhouse  into  a 


water:  source,  properties,  and  relation  to  life.  63 

shallow  pool,  in  which  one  or  two  cows  frequently  seek  com- 
fort. The  water  has  become  rich  in  organic  matter  and  sup- 
ports a  thick  growth  of  tiny  plants;  the  stones,  even,  may  be 
coated  with  green  slime.  This  vegetation  serves  as  a  warning 
to  the  hunter  and  the  w^oodsman,  who  wisely  drink  only  of 
water  from  clear  pools  with  bottom  of  shining  sand.  The 
heavy  material  stirred  up  by  the  cattle  soon  settles,  leaving 
the  water  in  the  stream  below^  clear,  although  probably  a  little 
yellow  in  color.  It  still  tastes  well  and  looks  all  right,  and 
may  be  used  by  human  beings  with  probable  impunity. 

Second:  The  little  stream  next  passes  other  farm  build- 
ings, where  the  privy  is  put  over  it  to  save  the  trouble  of 
cleaning,  or,  even  if  not  so  close,  is  placed  in  such  a  way  as  to 
allow  of  a  possible  wash  into  it,  especially  in  times  of  sudden 
rain. 

A  case  of  typhoid  fever  develops  at  this  farm.  No  pre- 
caution is  taken  to  disinfect  the  discharges,  and  a  portion  of 
the  dangerous  material  is  carried  into  and  along  with  the 
water.  Some  two  or  three  miles  below,  anolher  farmhouse, 
having  no  spring,  uses  this  same  little  stream  for  its  supply, 
perhaps  damming  it  up  into  a  little  pond  or  pumping  it  into 
a  tank.  All  unconscious  of  what  has  happened  above,  or 
ignorant  of  consequences,  this  water  with  a  history  is  -freely 
used,  and  perhaps  the  whole  family  come  down  with  the  dis- 
ease, perhaps  only  the  delicate  one  may  have  it.  It  may  be 
that  they  will  all  escape,  owing  to  the  fact  that  they  were 
particularly  robust,  or  that  they  drank  no  water  raw,  or  that 
the  conditions  on  the  stream  have  been  favorable  to  purifica- 
tion of  the  water  by  storage  and  consequent  growth  of  the 
green  plants,  which  are  our  friends  in  such  cases;  but  if  the 
water  were  pumped  into  a  covered  tank  and  used  soon  after, 
the  chances  are  nine  to  one  that  some  deleterious  results 
follow^ed. 


64  AIR,    WATER,    AND    FOOD. 

Third:  A  part  of  the  water  sinks  through  the  sand,  and  by 
this  filtration  becomes  freed  from  all  suspended  matter  and 
consequently  from  the  germs  of  disease,  if  present.  In  its 
course  if  it  is  intercepted  and  collected  in  a  shallow  well  it 
may  again  be  of  great  organic  purity  and  free  from  danger, 
but  it  will  surely  bear  the  telltale  marks  of  its  progress  in 
the  increase  of  chlorine  and  solids  which  will  have  escaped 
all  the  agents  of  purification,  and  in  the  nitrates,  the  result  of 
the  process. 

It  will  be  noticed  that  it  is  only  after  contamination  with 
the  ''  waste  of  human  life  "  that  danger  comes  to  other  human 
beings  and  that  many  circumstances  modify  that  danger. 
The  chances  are  about  equal  to  those  of  fire;  and  as  most 
householders  think  it  worth  while  to  insure  against  possible 
fire,  so  they  should  hold  the  chemist's  certificate  as  a  sort  of 
water  insurance;  but  since  the  fire  policy  does  not  protect 
from  carelessness,  the  knowledge  that  the  water-supply  is 
once  good  does  not  absolve  the  householder  or  the  citizen 
from  the  greatest  care  in  protecting  his  premises.  Duty  to 
his  neighbor  should  lead  him  to  see  that  this  coin  of  the 
world  is  passed  on  in  as  good  condition  as  possible,  and  he 
should  at  least  give  notice  of  danger  when  he  knows  that  it 
exists. 

But  this  general  movement  of  water  on  and  near  the  sur- 
face is  not  all  the  story.  From  25  to  40  per  cent,  of  the 
annual  rainfall,  in  temperate  regions,  soaks  at  once  into  the 
ground,  and  passing  downward  through  the  soil  to  hard-pan, 
to  clayey  or  impervious  layers,  or  to  rock  surface,  thence 
through  crevices,  broken  joints,  or  glacial  drift-deposits  to 
the  water-table,  flows  along  the  slope  for  many  miles,  until 
it  finds  its  way  again  to  the  surface,  either  from  the  bottom 
of  a  lake,  the  bed  of  a  river,  the  side  of  a  hill,  supplying  wells 
or  appearing  as  a  spring  free  from  all  organic  and  suspended 


water:    source,  properties,  and  relation  to  life.  65 

matter  but  often  rich  in  gases.  In  any  one  of  these  courses 
it  may  be  intercepted  by  man  and  caught  or  pumped  for  his 
use.  Such  water  may  never  have  been  far  from  the  surface;, 
it  may  have  been  used  and  returned  to  the  ground  many 
times;  it  may  have  appeared  as  surface-water  and  again  dis- 
appeared to  great  depths.  It  has  been  estimated  that  water 
moves  in  the  ground  at  rates  varying  from  0.2  to  20  feet  per 
day.  This  long  contact  with  rocks  will,  of  course,  bring  min- 
eral substances  into  solution  which  may  be  precipitated  as 
new  rocks  are  reached  or  other  streams  encountered,  so  that 
the  same  gallon  of  water  may  have  had  many  stages  in  its 
course  and  may  have  held  many  different  substances  in  solu- 
tion. An  example  of  how  much  can  be  so  held  is  found  in 
the  waters  of  the  alkali  belt  (page  241). 

It  is  no  wonder  that  so  active  a  solvent  as  water  should 
take  with  it  much  substance  whenever  it  remains  long  in  con- 
tact with  soil  or  rock,  for  it  may  be  many  months  before  that 
which  has  once  sunk  out  of  sight  again  appears.  In  fact,  great 
rivers  are  supposed  to  flow  into  the  sea  from  under  the  sur- 
face. 

Then,  too,  the  acquisition  of  dissolved  gases  favors  the 
solution  of  many  substances;  for  instance,  water  carryings 
carbon  dioxide  dissolves  limestone  as  well  as  lead  and  cop- 
per, and  when  at  low  temperature  and  containing  ammo- 
nium carbonate  water  may  dissolve  ferric  iron. 

Water  carrying  organic  acids  dissolves  among  other  sub- 
stances iron  compounds  which  may  or  may  not  be  in  the 
ferrous  condition,  and  therefore  may  or  may  not  be  precipi- 
tated on  coming  to  the  surface.  x\nd  as  w^e  have  seen  that 
the  ground  below  a  certain  level  is  permeated  with  moving 
water,  whatever  is  buried  in  the  earth  is  likewise  liable  to  enter 
the  watercourses  in  one  form  or  another. 

An   understanding   of   this    movement    of  water   under- 


56  AIR,    WATER,    AND    FOOD. 

ground,  with  tlie  accompanying-  changes  in  its  character, 
cannot  be  too  strongly  hisisted  upon,  for  the  lack  of  com- 
prehension of  it  is  at  the  root  of  most  of  the  troubles  from 
well-waters.  For  example,  the  leaching  cesspool,  the  primi- 
tive "  septic  tank,"  delivers  its  more  or  less  filtered  water  rich 
in  nitrogen  compounds  into  the  general  circulation  at  a 
depth  below  the  most  efficient  action  of  the  nitrifying  or- 
ganisms, hence  it  may  permit  the  passage  of  organisms  of 
putrefaction  into  underground  streams  or  into  the  well,  when 
access  is  direct.  Even  when  filtration  is  perfect,  the  products 
of  decay  are  yet  carried  with  it  and  so  tell  the  story  of  the 
past.  The  difficulty  is  to  determine  the  state  of  the  filter 
which  may  be  on  a  neighbor's  land  many  hundred  feet  away, 
and  to  be  sure  that  its  action  is  uniform.  Experience  with 
artificial  filters  shows  how  difficult  it  is  to  maintain  efficiency 
with  rapid  use;  hence  heavy  rains  or  wet  years  may  cause  a 
state  of  danger  not  ordinarily  existing. 

The  relation  of  water  to  human  health  must  be  consid- 
ered chiefiy  in  the  light  of  the  changes  which  go  on  in  the 
substances  held  suspended  or  dissolved  in  it,  and  the  effect 
of  these  changes  on  the  wholesomeness  of  the  water.  The 
suspended  matter  may  be  either  inert,  as  clay  or  sand;  dead 
vegetable,  as  fragments  of  plants;  living  vegetable,  as  plants 
floating  on  the  surface,  diatoms,  desmids,  algae,  etc.;  dead  or 
living  animal,  as  infusoria,  small  crustaceans,  etc. 

Wherever  these  occur  there  are  found  the  lower  orders 
of  vegetable  organisms,  fungi,  moulds,  bacteria,  ready  to  do 
the  necessary  work  of  decomposition  preparatory  to  solu- 
tion. The  mere  presence  of  these  forms  of  living  matter 
does  not  of  itself  niean  danger  to  those  using  the  water,  but 
among  these  may  be  found  pathogenic  organisms  which  are, 
at  present,  considered  as  liable  to  cause  disease.  Such  mi- 
■crobes  do  not  find  in  water  a  congenial  habitat,  and,  fortu- 


water:    source,  properties,  and  relation  to  life.  67 

nately,  do  not  thrive  on  the  vegetable  diet  and  in  the  cool  tem- 
perature of  natural  waters,  hence  the  other  organisms  soon 
overpower  them;  danger  decreases  not  only  in  proportion  to 
distance,  time,  and  dilution,  but  also,  probably,  to  the  abun- 
dance of  other  vegetable  life.  Under  favorable  circum- 
stances the  danger  is,  however,  a  very  real  one. 

The  presence  of  certain  living  plants  may,  moreover,  give 
rise  to  unpleasant,  if  not  dangerous,  tastes  and  odors,  due  to 
the  presence  of  extremely  pungent  oils  or  other  aromatic 
substances  formed  in  the  process  of  growth.  When  these 
plants  are  decaying  putrefactive  odors  are  also  present,  some- 
times rendering  the  water  too  offensive  for  use.  These  or- 
ganisms are  described  in  Whipple's  ''  Microscopy  of  Drink- 
ing-water," and  in  Chapter  VII  a  short  list  of  those  which 
give  characteristic  odors  will  be  found. 

The  presence  of  much  decaying  vegetable  matter  in 
drinking-water  is  to  be  avoided,  since  it  is  not  known  what 
€fTect  it  may  have  upon  the  general  health  of  the  individual, 
rendering  him  perhaps  more  susceptible  to  disease. 

Food-supply  is  a  necessary  condition  for  life,  and  there 
cannot  be  abundant  growth  in  a  water  without  a  correspond- 
ingly large  amount  of  dissolved  substances  furnishing  the  food 
for  this  living  fauna  and  flora.  As  has  been  stated,  water 
usually  carries  considerable  mineral  substance  and  is  often 
supplied  with  organic  and  gaseous  compounds,  while  nitro- 
gen is  furnished  from  many  sources,  most  abundantly  from 
sewage,  so  that  it  is  not  strange  that  water-life  is  so  abundant, 
but  rather  that  it  is  not  more  so.  Most  of  the  difficulties  in 
securing  a  satisfactory  water-supply  are  connected  with  the 
cycle  of  nitrogen  in  its  relation  to  organic  life. 

This  may  be  briefly  stated  as  follows:  Nitrogen  is  found 
as  an  essential  constituent  of  all  living  matter.  When  thus 
combined,  it  is  the  so-called  organic  nitrogen,  and  is  found 


68  AIR,    WATER,    AND    FOOD. 

in  undecomposed  vegetable  or  animal  substances.  As  soon  as 
dead,  these  substances  may  become  food  for  micro-organisms 
and  the  nitrogen  then  appears  in  a  form  from  which  it  can  be 
obtained  as  ammonia;  for  instance,  from  decaying  beans,  from 
putrefying  broth,  and  from  fresh  sewage.  This  process  takes 
place  with  or  without  much  air  and  may  be  accompanied  by 
very  bad  odors.  As  soon,  however,  as  the  nitrogen  has  passed 
from  the  insoluble  organic  form  into  the  soluble  compounds 
from  which  ammonia  is  obtained,  then,  if  oxygen  is  present, 
and  only  then,  another  set  of  micro-organisms  take  up  the 
work  and  nitrites  appear;  when  still  another  set  have  done 
their  work  the  nitrogen  is  found  only  in  combination  as  ni- 
trates, fully  oxidized  and  mineralized,  no  longer  organic  or 
capable  of  sustaining  the  life  of  the  lower  forms  of  vegetation, 
but, on  the  other  hand,  the  most  valuable  food  for  chlorophyll- 
bearing  plants  which  convert  nitrates  again  into  organic 
nitrogen.  This  cycle  may  be  arrested  or  broken  at  certain 
stages.  If  the  soluble  ammonia  compounds  are  set  free  out 
of  contact  with  air  or  below  the  layers  of  soil  containing  the 
nitrifying  organisms,  they  may  remain  indefinitely  un- 
changed. If  nitrates  have  been  carried  below  the  reach  of 
the  roots  of  the  chlorophyll-bearing  plants,  or  if  they  are  con- 
fined in  a  space  deficient  in  oxygen,  then  an  access  of  decom- 
posable organic  matter  with  micro-organisms  will  cause  a 
reduction  of  the  nitrates  to  nitrites  and  free  nitrogen,  through 
the  action  of  these  lower  plants  which,  in  the  absence  of 
air,  take  the  little  oxygen  they  need  from  mineral  com- 
pounds. 

These  micro-organisms  are  not  the  only  ones  at  work, 
however.  In  any  sudden  prominence  of  one  factor  others 
are  apt  to  be  overlooked;  thus  in  the  present  case  the  in- 
finitely small  has  so  powerfullv  aiYec'ed  men's  minds  thaS 
partly  because  the  micro-organisms  are  beyond  their  range 


WATER:     SOURCE,    PROPERTIES,    AND    RELATION    TO    LIFE.   69 

of  vision,  such  forms  of  life  as  are  evident  to  the  naked  eye 
or  with  low  powers  of  the  microscope  have  been  overlooked 
to  an  extent. 

As  agents  of  putrefaction  and  of  decay  the  micro-organ- 
isms have  their  work  to  do,  but  the  final  purification — the 
finishing  up  of  the  work — belongs  to  another  order  of  life. 
The  still  minute  but  visible  green  plants — those  which  fioat 
free  in  water  or  attach  themselves  to  larger  growths — have 
now  their  part  to  play.  The  life-history  of  these  forms  has 
been  little  studied,  and  the  work  they  do  in  the  actual  puri- 
fying of  polluted  water  has  been  almost  overlooked.  The 
impression  left  on  reading  most  books  is  that  when  foul  mat- 
ter has  been  dissolved  and  converted  into  ammonia,  carbon 
dioxide,  and  nitrates  the  work  is  done,  but  these  compounds 
only  furnish  food  for  the  next  class,  and  these  again  for  in- 
fusoria, tiny  crustaceans,  etc. 

In  some  cases  these  organisms  succeed  each  other  with 
great  rapidity;  in  one  case  the  fauna  and  flora  of  a  given 
pond  varied  each  week  of  a  season,  certain  rare  forms  being 
found  only  once. 

There  is  needed,  almost  more  than  anything  else,  a  con- 
secutive study  of  the  green  plants  found  in  water-supplies, 
since  by  their  cultivation  greater  purity  might  be  attained 
and  possibly  a  way  might  be  found  of  exterminating  the  dis- 
agreeable ones.  The  most  unexpected  results  may  follow 
the  long  study  of  a  single  organism,  such  as  has  been  given 
to  Oscillaria  prolijica  of  Jamaica  Pond  for  a  period  of  fifteen 
years.  Weekly,  sometimes  daily,  observations  have  been 
made  for  several  years.* 

It  is  organisms  of  this  class  which  give  tastes  and  odors 
to  water,  and  which,  if  enough  were  known  concerning  them, 

*  Trans.    A.    A.   A.    S.,    1898.      Technology    Quarterly^    14    (^igoi),   302;   15 
{igo2\  308. 


70  AIR,    WATER,    AND    FOOD. 

would  probably  give  perfectly  trustworthy  evidence  as  to  the 
past  history  or  source  of  contamination. 

The  two  classes  of  organisms  work  in  opposite  directions^ 
and  so  long  as  food  is  present  for  either,  life  will  increase  with 
proportional  rapidity.  This  connection  of  cause  and  elTect 
should  be  made  familiar  to  the  intelligent  citizen.  When  a 
ground-water  free  from  all  organic  mat'er  but  rich  in 
nitrates  is  exposed  in  an  open  basin  the  rich  growth  of 
chlorophyll-bearing  algse  follows  as  a  matter  of  course;  later^ 
decay  sets  in  and  products  of  decomposition  abound,  the  air 
above  being  the  source  of  a  constant  supply  of  spores  of  all 
kinds. 

\Mien  a  house-  or  barn-drain  empties  into  a  small  slug- 
gish stream,  it  soon  becomes  filled  with  green  plants  thriving 
on  the  ammonia,  and  it  is  often  possible  to  trace  the  source 
of  pollution  of  a  large  lake  by  the  line  of  green  anabasna 
leading  to  the  insignificant  ditch. 

A  curious  blindness  on  the  part  of  managers  of  water- 
works to  the  movements  of  water  and  its  action  in  transport- 
ing material  is  seen  not  only  in  the  almost  universal  proximity 
of  cemeteries  to  reservoirs,  but  also  in  the  common  practice 
of  dressing  the  sloping  banks  of  turf  with  a  heavy  coating  of 
manure.  Even  if  this  was  derived  from  clean  stables  and 
was  not  liable  to  be  contaminated  w^ith  night-soil,  the  abun- 
dant food  for  plants  which  inevitably  finds  its  way  into  the 
reservoir  occasions  as  fruitful  results  in  the  water  as  on  the 
banks,  and  is  undoubtedly  the  cause  of  much  of  the  trouble 
in  storage  basins. 

It  is  evident,  therefore,  that  a  once  polluted  water  cannot 
be  said  to  be  purified  so  lone:  as  food  for  green  planLs  re- 
mains, for  the  moment  the  temperature  and  other  conditions 
become  favorable  growth  will  beo^in.  The  term  "  purifica- 
tion," taken  in  a  chemical  sense,  should  not  be  looselv  used. 


water:   source,  properties,  and  relation  to  life.  71 

Complete  purification  can  take  place  only  when  all  traces  of 
former  impurity,  in  any  form,  have  been  removed.  Chemical 
precipitation  of  sewage  leaves  the  soluble  ammonia,  and  sand 
filtration  leaves  nitrates  to  serve  for  abundant  life  and  sub- 
sequent decay  in  the  streams  into  which  the  effluents  flow. 
Such  effluents  are  clarified  and  the  organic  matter  may  have 
been  mineralized,  but  this  is  not  purified  water.  Only  when 
growing  plants  have  removed  this  food  and  have  themselves 
been  removed  can  the  water  approach  a  purified  condition. 

The  effect  of  storage  of  water  containing  high  nitrates 
in  open  tanks  or  reservoirs  exposed  to  the  collection  of  dust 
will  be  that  spores  of  chlorophyll-bearing  alg^e,  diatoms, 
desmids,  etc.,  will  soon  develop  and  will  increase  as  long^as 
the  food  (nitrates,  mineral  matter,  etc.)  lasts.  Only  by  pro- 
tection from  dust  and  light  can  such  water  be  kept  free 
from  unpleasant  accumulations  of  suspended  organisms  or 
from  disagreeable  tastes.  Unpolluted  surface-w^aters,  on  the 
other  hand,  improve  on  storage,  as  a  general  rule,  if  the  basin 
is  a  clean  one.  The  storage  of  polluted  or  clarified  water  is 
thus  forbidden,  since  not  infrequently  the  first  indication  of 
the  pollution  of  a  surface  supply  is  given  by  the  appearance 
of  some  member  of  that  richly  nitrogenous  group  of  algae 
called  cyanopJiycece,  or  ''  blue-greens/'  from  the  presence  of 
blue  or  purple  coloring  matter  along  with  the  yellow-green 
chlorophyll.  Since  this  group  of  plants  contains  from  seven 
to  eleven  per  cent,  of  nitrogen,  while  other  groups  contain 
only  one  or  two,  it  is  evident  that,  if  it  is  to  flourish,  more 
nitrogenous  food  must  be  supplied.  This  may  be  derived 
from  fertilized  fields,  from  decay  of  other  vegetable  life,  as 
well  as  from  the  richer  source  of  direct  sewage:  but,  in  anv 
case,  the  growth  of  these  plants  is  a  sign  of  abundant  food- 
supply  which  must  be  cut  ofif  if  they  are  to  be  starved  out,  as 
they  must  be  unless  they  are  removed  while  fresh  by  strain- 


■^2  AIR,    WATER,    AND    FOOD. 

ing  or  skimming,  for  the  odor  of  their  decay  s  so  intolerable 
as  to  preclude  the  use  of  the  water.  In  some  cases  the  odor 
accompanying  their  growth  renders  the  water  quite  objec- 
tionable, and  neither  natural  nor  artificial  filtration  is  able  to 
remove  it. 

Either  natural  or  artificial  basins  may  have  a  collection  of 
vegetable  matter  on  the  bottom  which  slowly  decomposes 
in  summer,  and  since  the  bottom  water  is  colder,  the  resulting 
ammonia  remains  until  the  late  fall  overturn,  when  it  is 
brought  to  the  surface,  where  it  favors  the  growth  of  diatoms 
and  other  cold-water  plants.  Certain  diatoms,  as  asterio- 
nella,  cause  disagreeable  odors.  Such  basins  show  the  least 
ammonia  in  early  October  and  the  most  in  late  November. 

In  order  to  make  any  predictions  as  to  the  pro'bable  de- 
velopment of  this  flora  and  fauna  of  water,  experience  and 
at  least  a  year's  watching  of  any  given  supply  are  required 
until  more  is  known  of  the  life-history  of  these  forms  of  life. 
Nothing  is  more  needed  to-day  than  work  along  these  lines. 
When  may  disagreeable  odors  and  tastes  be  expected? 
What  precaution  or  measures  may  be  taken  in  each  case  to 
prevent  them?  These  are  the  questions  the  water-works 
superintendent,  equally  with  the  consumer,  is  asking,  for  the 
most  part  vainly  as  yet. 

As  has  been  stated,  surface-waters  often  carry  stable  or- 
ganic matter  in  connection  with  color,  so  that  while  the 
organic  nitrogen  shows  high,  no  free  ammonia  or  nitrates  are 
formed  on  standing.  These  w^eak  meadow-teas  are  now 
largely  used  for  town  supplies,  and  a  word  as  to  the  source 
of  the  color  may  not  be  amiss.  Many  carbonaceous  sub- 
stances, sugar,  for  example,  when  partially  broken  up  become 
caramelized  and  give  a  brown  solution,  the  color  being  due 
to  substances  richer  in  carbon;  this  color  is  deeper  as  the 
decomposition  is  more  complete.     There  is  no  reason  to  sup- 


water:   source,  properties,  and  relation  to  life.  "J^i 

pose  that  such  compounds  have  any  deleterious  effect  on 
health.  Indeed,  experience  has  proved  that  such  waters  are 
more  reliable  than  many  others. 

The  chlorine  of  unpolluted  natural  waters  is  derived  from 
the  sea  in  past  or  present  times.  Waves  breaking  on  a 
rocky  shore  send  finely  divided  salt-spray  high  into  the  air; 
dust-particles  becoming  coated  with  it  carry  their  burden  of 
salt  around  the  world.  The  rain  brings  to  earth  now  more, 
now  less  of  this  salted  dust,  each  region  receiving  in  the 
course  of  the  year  an  amount  fairly  proportional  to  its  dis- 
tance from  the  seacoast  and  to  the  rainfall.  No  mountain 
lake  or  stream  has  yet  been  found  free  from  this  element. 
Where  evaporation  and  rainfall  nearly  balance,  the  normal 
chlorine  will  be  that  of  the  rain  for  the  year,  but  where  evapo- 
ration is  in  excess  it  may  exceed  that  for  any  given  year.  In 
the  absence  of  salt-springs  and  industries  using  much  salt, 
the  source  of  chlorine  in  excess  of  the  normal  is  the  do- 
mestic life  of  man.  Mr.  F.  P.  Stearns  has  estimated  that  the 
chlorine  in  the  annual  drainage  of  any  watershed  is  increased 
one-tenth  part  per  million  by  20  inhabitants  per  square  mile. 

Chlorine  may  serve  to  prove  not  only  the  presence  but 
the  amount  of  sewage  pollution  in  any  case  where  the  other 
factors  are  known.  Otherwise  chlorine  has  no  sanitary 
significance. 

Of  the  mineral  constituents  in  waters  there  is  little  to 
say  except  that,  like  climate,  water  is  to  be  taken  as  It  is 
found — hard,  high  in  mineral  matters  if  derived  from  a  lime- 
stone region,  soft  if  from  archean  formations.  Physicians  are 
not  agreed  as  to  the  effects  of  hard  water,  or  of  the  brown 
soft  waters. 

Fortunately  the  human  system  possesses  remarkable 
adaptability,  so  that  if  slowly  accustomed  to  a  given  condi- 
tion, as  we  have  seen  in  the  case  of  air,  and  as  we  shall  have 


74  AIR,    WATER,    AND    FOOD. 

occasion  to  remark  when  food  is  considered,  it  can  safely 
bear  what  would  be  a  serious  shock  if  suddenly  encountered 
from  an  opposite  condition.  Natives  of  a  hard-water  region 
are  made  ill  on  coming  to  a  soft-water  region,  and  vice  versa. 
Inhabitants  of  a  city  with  a  polluted  water-supply  seem  to 
acquire  a  certain  immunity. 

The  safety  from  organic  contamination  secured  by  the 
use  of  distilled  water  has  brought  up  the  question  of  a  pos- 
sible danger  in  too  little  mineral  contents  for  the  best  cellular 
interchange  wherein  lies  life. 

With  the  superabundance  of  mineral  salts  in  ordinary 
diet,  there  would  seem  to  be  little  cause  for  alarm;  but  if  the 
food  were  poor  in  these  substances,  it  is  quite  conceivable 
that  evil  results  might  follow  a  free  use  of  distilled  water. 

A  word  as  to  the  care  of  water  in  the  house  may  not 
seem  amiss,  in  view  of  the  tendency  it  has  to  absorb  gases, 
to  collect  dust,  to  favor  chemical  and  vital  changes,  to  dis- 
solve metals. 

Too  great  care  cannot  be  taken  in  all  these  directions  to 
secure  water  freshly  drawn  from  the  main  pipe  beyond  the 
lead  or  brass  house-pipes  and  to  avoid  those  traps  for  the  un- 
wary householders — faucet  filters. 

When  the  w^ater-supply  is  cafe,  but  warm  and  flat  to  the 
taste,  ice  is  frequently  used  to  cool  it. 

Much  has  been  said  about  the  dangers  of  ice  when  used 
in  drinking-water  and  on  or  about  food.  The  latter  is  prob- 
ably the  most  serious  danger,  since  people  are  not  so  careful 
about  the  quality  of  ice  for  that  purpose. 

Certain  rules  may  be  broadly  stated  as  guides  to  the 
householder: 

Crystal-clear  ice,  free  from  crevices,  bubbles,  etc.,  is 
probably  pure,  for  it  has  been  formed  from  slow  freezing  in 
a  thin  layer,  over  a  deep  mass  of  water,  as  20  to  30  inches  of 


water:  source,  properties,  and  relation  to  life.  75 

ice  in  a  pond  40  or  60  feet  deep.  In  this  case  the  impurities 
have  been  excluded.  This  crystal  ice  is  impermeable  to  air 
and  therefore  to  what  air  carries,  and  of  course  to  water 
and  what  it  carries. 

An  equally  safe  rule  is  to  discard  all  "snow-ice"  made 
from  snow  saturated  with  water. 

The  increasing  difficulty  of  obtaining  safe  water  has? 
caused  an  increasing  use  of  distilled  water  obtained  either 
from  domestic  stills  or  in  bottles  or  carboys  from  manu- 
facturers. The  latter  is  often  a  desirable  source  of  drink- 
ing-water if  the  glass  does  not  scale  off  from  the  bottles. 
A  very  little  common  salt  may  be  added  if  the  consumer 
prefers,  or  even  a  drop  or  two  of  the  druggists'  "lime- 
water." 

The  domestic  still,  if  made  from  a  poor  quality  of  metal, 
may  bring  an  evil  second  only  to  that  of  polluted  water. 
Lead  should  not  enter  into  its  construction. 


CHAPTER  VI. 

THE    PROBLEM    OF    SAFE    AND    ACCEPTABLE    WATER    AND    THE 
INTERPRETATION    OF    ANALYSES. 

{From  the  Chemist's  Standpoint.) 

From  what  has  been  said  it  will  be  evident  that  the  prob- 
lem of  safe  water  for  domestic  use  is  not  so  much  concerned 
with  the  water  itself  as  with  its  property  as  a  carrier  and  its 
part  in  chemical  changes. 

We  have  seen  how  a  great  variety  of  vegetable  and  ani- 
mal matter  finds  its  way  into  the  water  of  a  settled  reg'on; 
and  as  it  is  constantly  being  transformed  from  one  form  to 
another  by  the  agency  of  multitudes  of  organisms,  it  is  evi- 
dent that  the  exigencies  of  modern  life  render  impossible  the 
exclusive  use  of  water  of  great  organic  purity.  It  is  useless, 
therefore,  to  fight  over  again  the  battles  of  the  past  as  to  the 
source  and  kind  of  ''  organic  matter  "  in  water. 

We  have  also  seen  that  it  is  not  the  mere  presence  of 
compounds  of  carbon,  hydrogen,  and  nitrogen  in  drinking- 
water  which  gives  the  element  of  danger.  It  is  not  even 
the  fact  that  these  have  taken  part  in  animal  life;  fish  and 
frogs  continually  die  in  ponds  and  streams,  to  say  nothing 
of  countless  cyclops  and  mosquito  larv^.  Well  authenti- 
cated cases  are  on  record  in  which  one  drink  of  a  polluted 
water  has  proved  fatal;  while,  on  the  other  hand,  it  is  equally 
sure  that  highly  contaminated  water  has  been  used  with  ap- 
parent impunity. 

76 


water:   the  problem  of  safe  water.  77 

When  water  has  received  excreta  of  diseased  human 
beings,  disease-germs  are  very  hkely  to  be  conveyed  by  it 
to  other  human  beings.  In  a  city  there  are  always  cases  of 
disease,  therefore  all  city  sewage  is  to  be  considered  danger- 
ous. But  besides  the  living  germs  there  are  other  accom- 
paniments of  decaying  organic  matter  which,  when  in  con- 
centrated form,  sometimes  show  toxic  properties.  Certain 
facts  and  many  conjectures  lead  to  the  conclusion  that  a 
water  is  "  safe  "  only  when  free  from  decaying  substances. 

Along  with  the  millions  of  harmless  micro-organisms 
engaged  in  the  work  of  conversion  there  may  be  a  few  score 
inimical  to  the  health  of  man,  and  for  the  education  of  the 
still  skeptical  public  it  is  often  advisable  to  speak  somewhat 
strongly  of  the  possible  dangers  from  water-borne  disease- 
germs. 

Nitrogen  as  the  Essential  Element  in  Lilting  Matter. — All 
organisms  from  the  lowest  to  the  highest  thrive  only  in  the 
presence  of  food;  therefore  only  that  organic  matter  which 
serves  to  support  life  or  which,  as  a  product  of  life,  may  be 
deleterious  to  man  is  rightly  to  be  held  as  dangerous.  The 
element  common  to  both  kinds  is  nitrogen;  .therefore  the 
water-analyst  seeks  evidence  not  only  of  its  presence  or  ab- 
sence, but  of  the  forms  in  which  it  is  found  and  their  relation 
to  one  another.  It  may  be  assumed  that  any  water  which 
shows  no  change  in  the  relative  amount  of  its  nitrogenous 
compounds  at  the  end  of  a  week  either  does  not  contain  the 
organisms  necessary  to  elYect  this  change  or  is  wanting  in 
the  food  upon  which  they  can  thrive.  As,  however,  It  is 
inconvenient  to  Avait  a  week  before  deciding  this  point,  other 
methods  are  used.  The  so-called  albuminoid  ammonia  is 
supposed  to  indicate  the  amount  of  decomposable  nitrogen- 
ous matter,  but,  as  a  matter  of  fact,  taken  by  itself  it  gives 
little  information  of  value.     While  its  absence  is  conclusive, 


^8  AIR,    WATER,    AND    FOOD. 

its  presence  is  not  equally  so;  but  a  proof  of  its  variability 
from  day  to  day  is  really  valuable.  Whether  used  in  the  final 
interpretation  or  not,  "  organic  nitrogen  "  (or  that  portion 
of  it  appearing  as  albuminoid  ammonia)  is  always  deter- 
mined, together  with  the  other  forms,  as  soon  as  the  sample  is 
received. 

A  nitrogenous  organic  compound  is  dangerous  from  one 
of  two  causes:  first,  because  it  is  alrcc^dy  decaying  and  har- 
bors pathogenic  germs  or  is  giving  off  toxines;  or,  second, 
because  it  will  furnish  food  for  a  further  development  of  bac- 
terial life. 

As  to  its  derivation  from  animal  or  from  vegetable  mat- 
ter, there  need  be  little  discussion,  especially  since  the  recog- 
nition of  the  high  nitrogenous  content  of  the  blue-green 
a\gx  and  the  nitrogenous  character  of  "  soil-humus  "  and 
the  close  approximation  of  animal  and  vegetable  protoplasm. 
But  it  is  most  important  to  know  if  it  is  stable,  since  one  of 
the  best  aphorisms  ever  contributed  to  the  literature  of  water- 
analysis  is  given  by  Dr.  Drown's  statement,  "  A  state  of 
change  is  a  state  of  danger." 

Results  of  the  Decay  of  Nitrogenous  Organic  Matter. — The 
products  of  the  first  stage  of  decay  of  this  class  of  organic 
matter  are  carbon  dioxide  and  ammonia.  It  is  to  the 
latter  that  we  turn  for  the  proofs  cought,  by  reason  of  the 
methods  at  hand  for  detecting  such  small  amounts  as  one 
part  in  a  billion  parts  of  water,  and  because  it  is  for  the  nitro- 
gen compound  that  we  seek. 

The  mere  presence  of  free  ammonia  is  not  a  suf^cient  in- 
dication of  recent  pollution  from  human  sources.  Rain-water, 
as  shown  in  Table  III,  contains  considerable  quantities; 
decaying  blue-green  algae  furnish  it  in  still  larger  amounts, 
and  moreover  it  offers  acceptable  food  to  plant-life  and  may 
therefore    disappear    in    the    form-    of    combined    nitrogen. 


WATER:  THE  TROBLEM  OF  SAFE  WATER.       79 

Nevertheless,  it  is  to  be  held  as  one  of  the  chief  witnesses,  for 
it  is  found  in  sewage  in  a  thousand  times  the  quantity  in 
which  it  occurs  in  ordinary  potable  water.  While  putrefac- 
tive decay  takes  place  by  stages,  the  lines  of  division  are  not 
sharply  drawn,  and  nitrites,  the  result  of  the  second  stage,  may 
be  and  usually  are  found  in  polluted  waters  together  with 
ammonia.  So  frequently  is  this  the  case  that  it  is  considered 
circumstantial  evidence  suf^cient  to  convict  when  both  am- 
monia and  nitrites  are  found  together.  (See  Tables  V  and 
VI,  p.  241.) 

The  reason  is  not  far  to  seek.  Both  are  not  only  prod- 
ucts of  decay,  but  both  are  in  that  unstable  condition  which 
indicates  active  processes,  and  which  therefore  means  the 
presence  of  micro-organisms.  Certain  exceptions  will  be 
noted  later. 

The  fourth  form  of  nitrogen,  that  found  in  nitrates,  is  no 
longer  classed  as  organic;  it  is  now  become  food  for  green 
plants  and  cannot  nourish  the  class  to  which  bacteria  and 
pathogenic  germs  belong,  hence  it  is  fair  to  presume  that  for 
lack  of  food  the  latter  have  succumbed  or  have  been  other- 
wise removed.  The  value  of  this  test  is  the  proof  it  sometimes 
furnishes  of  previous  sewage  pollution,  since  the  nitrogen 
present  in  excess  of  that  brought  down  by  rain  must  have 
been  furnished  either  by  fertilizers,  by  decaying  matter,  or  by 
sewage.    (See  Tables  V  and  VI,  p.  241.) 

Organic  Carbon. — Since  by  far  the  largest  constituent  of 
organic  matter  is  carbon,  some  fifty  per  cent.,  it  might  seem 
as  if  this  was  the  best  indication  of  pollution.  Indeed,  it  was 
formerly  so  considered,  and  many  methods  have  been  de- 
vised to  show  its  presence  quantitatively.  As  our  knowledge 
of  the  slight  differences  between  many  forms  of  animal  and 
vegetable  substances  grows,  the  probability  of  any  conclusive 
evidence  from  this  source,  either  as  to  past  history  or  present 


8o  AIR,    WATER,    AND    FOOD. 

condition,  decreases.  In  short,  although  for  many  years 
water-analysts  have  been  striving  to  perfect  methods  of  de- 
tecting certain  substances  and  certain  organisms,  it  would 
seem  as  if  they  were  no  nearer  a  discovery  of  one  simple  de- 
cisive test,  but,  in  most  cases,  were  driven  to  a  somewhat 
elaborate  examination  in  which  one  test  only  furnishes  one 
link  in  the  chain  of  evidence. 

Sanitary  Analysis. — The  examination  of  a  water  to  deter- 
mine its  safety  for  domestic  use  is  called  a  sanitary  analys's, 
in  distinction  from  that  examination  which  determines  its 
fitness  for  manufacturing  purposes,  for  use  in  steam-boilers, 
or  its  medicinal  value. 

Four  points  are  to  be  determined:  First,  the  amount,  if 
any,  of  organic  matter  in  a  living  or  dead  condition,  sus- 
pended or  dissolved  in  the  water;  second,  the  amount  and 
character  of  the  products  of  decomposition  of  organic  mat- 
ter, and  their  relative  proportions  to  one  another;  third,  the 
stability  of  the  undecomposed  organic  substances;  fourth, 
the  amount  of  certain  mineral  substances  dissolved.  From 
these  results  we  draw  conclusions  as  to  the  present  condition 
and  past  history  of  the  water.  These  conclusions  are  not  in- 
fallible, but  there  are  enough  unavoidable  risks  in  human 
life  without  taking  unnecessary  ones;  and  if  pollution  is 
proved,  the  cause  should  be  removed  or  the  supply  aban- 
doned. 

Preliminary  Inspection. — So  long  as  the  eye  can  re-enforce 
the  other  tests  and  the  whole  course  of  the  water  may  be 
clearly  traced,  it  is  comparatively  easy  to  judge  of  the  charac- 
ter of  a  supply  and  of  its  safety  for  human  use;  but  when  a 
hole  in  the  ground  is  the  visible  source,  or  the  actual  history 
of  the  water  is  hidden  in  unknown  distances  and  depths,  the 
diagnosis  is  more  difficult. 

First,  the  geological  horizon  and  superficial  soil  must  be 


WArKk:    rnK  problem  of  safe  water.  8i 

studied;  the  direction  and  flow  of  underground  water,  not  the 
slope  of  the  surface  only;  the  possible  sources  of  danger, 
occasional  as  well  as  constant,  within  at  least  a  quarter  of  a 
mile  radius.  The  composition  of  unpolluted  water  of  the 
same  region  should  always  be  at  hand  for  consultation. 

Sate  Wafer. — As  has  been  said,  we  can  no  longer  require 
pure  water;  the  most  that  we  can  demand  is  that  the  supply 
shall  be  safe.  To  the  uninitiated  one  sample  of  clear,  color- 
less water  seems  very  like  any  other.  The  safe,  colored  or 
muddy  water  of  a  stream  or  pond  seems  less  desirable  than 
the  clear,  cold  water  of  a  badly  polluted  well. 

A  water  may  be  normally  safe  and  yet,  from  exceptional 
circumstances,  be  for  a  time  a  source  of  danger.  In  one  case 
the  mouth  of  a  well  at  a  factory  was  overflowed  by  a  con- 
taminated brook  raised  above  its  usual  level  b^^  a  heavy 
shower  for  half  an  hour  only.  Some  thirty  cases  of  typhoid 
fever  resulted,  so  close  to  one  another  and  so  sudl^^nV  ceas- 
ing as  to  leave  no  doubt  of  the  fact  that  for  only  a  few  hours 
was  the  water  unsafe.  How,  then,  shall  a  chemist  tell  if  at 
some  past  time  a  water  may  have  been  or  at  some  future  time 
may  become  a  source  of  disease?  Only  by  carefullv  weigh- 
ing all  the  testimony  attainable — ocular,  chemical,  biological^ 
bacteriological — in  the  light  of  past  experience. 

The  day  of  the  vest-pocket  sample,  usually  in  a  f^avorins:- 
extract  bottle,  cork  and  all,  is  nearly  past,  but  that  of  ^he 
fruit-jar,  with  a  sticky  rubber  ring  and  corroded  zinc  top.  is 
still  with  us.  That  admiration  for  chemical  knowledg^^  and 
belief  in  chemical  clairvoyance  which  expects  the  chemist  to 
decide  from  a  sample  while  you  wait  if  a  certain  water  causerl 
the  death  of  a  person  a  month  since  in  a  distant  town  unde- 
unknown  conditions  is  very  trying  to  the  man  who  knows  his 
own  limitations. 

The  market  value  of  an  analysis  cannot  well  be  appre- 


Sz  AIR,    WATER,    AND    FOOD. 

ciated  until  a  juster  estimate  of  the  professional  training  of 
the  analyst  is  a  part  of  common  knowledge. 

Safe  and  Acceptable  Water. — It  is  not  enough  that  a 
supply  shall  be  free  to-day  from  disease-germs;  it  should  re- 
main free  from  changes  for  a  reasonable  period  of  time. 
Therefore  the  advice  desired  by  the  towns  seeking  for  sup- 
plies implies  much  more  than  mere  analysis;  it  includes  esti- 
mates of  future  changes,  of  variations  due  to  possible  further 
•developments,  and  of  the  effect  of  these  variations  on  accept- 
ability as  well  as  safety. 

To  be  fully  acceptable,  a  water  should  be  free  from  color, 
odor,  turbidity,  sediment,  and  of  a  uniform  temperature  so 
low  as  to  admit  of  use  without  ice.  Only  such  water  as  has 
been  earth-filtered  and  earth-cooled  can  meet  this  demand, 
but  the  supply  of  this  class  is  becoming  drawn  upon  to  its 
limit;  besides  there  are  difficulties  in  the  conveyance  and 
•Storage  of  ground-water  which  offset  many  of  its  advantages. 

From  the  foregoing  paragraphs  it  will  be  seen  not  only 
that  waters  carry  every  possible  degree  of  safety  or  danger 
according  to  the  country  they  drain,  the  num'ber  and  habits 
of  the  people  living  on  the  watershed,  and  the  presence  or 
absence  of  factories,  slaughter-houses,  etc.,  but  that  many 
elements  enter  into  the  judgment  of  a  water-supply,  and  how 
different  these  elements  are  in  different  waters.  Safe  water 
is  that  which  carries  neither  seeds  of  disease  nor  such  sub- 
stances as  are  deleterious  in  any  way  to  mankind  in  general. 

A  brown  water  may  yield  20  parts  per  million  organic 
matter  and  show  10  parts  oxygen  consumed,  and  yet  be  a 
safe  and  wholesome  water.  A  ground-water  may  show  5 
parts  nitrates,  and  yet  for  ten  or  twenty  years  prove  a  safe 
supply. 

Since,  however,  water  is  so  universally  made  a  carrier  of 
refuse,  it  is  difificult  to  find  a  stream  or  well  which  fulfils  the 


water:    the  problem  of  safe  water.  8^ 

above  exacting  requirements,  and  a  compromise  is  made 
which  sets  certain  arbitrary  limits  and  so  keeps  the  chances 
small.  Such  limits  are  very  misleading  of  themselves,  espe- 
cially if  used  over  a  wide  extent  of  territory.  The  English 
standards,  for  instance,  are  not  applicable  to  eastern  North 
America.  Only  a  study  of  all  local  conditions  and  a  wise  in- 
terpretation of  all  results  can  make  standard  figures  of  any 
significance.  This  is  true,  also,  of  bacterial  results  in  surface- 
waters.  In  the  natural  condition  of  lakes  and  streams  there 
are  so  many  varieties  of  bacteria  present  and  in  such  varying 
numbers,  according  to  wind  and  rain  and  watershed,  that 
taken  alone  the  numerical  count  gives  no  more  convincing 
proof  than  is  found  in  chemical  figures. 

While  it  is  quite  within  the  limits  of  possibility  that  a 
culture-tube  of  typhoid  bacilli  might  be  emptied  into  the 
middle  of  a  river  or  be  washed  into  a  reservoir,  and  chemical 
analysis  give  no  sign,  yet  no  continuous  natural  means  of 
contamination  is  known  which  is  not  accompanied  by  sub- 
stances readily  detected  by  suitable  chemical  examination. 
In  either  case  an  epidemic  may  or  may  not  result,  dependent 
upon  causes  other  than  the  mere  presence  or  absence  of  the 
micro-organisms. 

If  drainage  from  a  house  or  barn  is  seen  entering  a 
stream,  it  does  not  need  a  dozen  plate-cultures  to  prove  that 
there  is  possible  danger.  Such  tests  may,  however,  when 
used  with  skill,  serve  to  trace  contamination  back  to  its 
source,  and  is  another  means  at  the  service  of  the  trained 
water-works  superintendent  whereby  he  can  keep  a  close 
watch  over  the  character  of  his  supply. 

As  a  means  of  control  of  the  efificiency  of  filter-plants  the 
bacterial  examination  is  invaluable,  and  as  a  knowledge  of 
the  forms  which  accompany  pathogenic  germs  becomes  more 
-certain   the   value   of  these   tests   will   increase,   even   if  the 


84  AIR,    WATER,    AND    P^OOU. 

classification  and  identification  is  not  perfected  to  scientific 
accuracy. 

It  is  one  of  the  penalties  of  living-  in  a  large  city  that  the 
water-supply  must  of  necessity  be  surface-water  which  has 
been  caught  and  stored  at  a  distance  or  that  which  has  been 
filched  from  a  stream,  filtered  and  made  passable.  Conse- 
quently education  must  take  the  place  of  instinct,  and  custom 
must  make  that  acceptable  which  circumstances  render 
necessary. 

THE    INTERPRETATION    OF   ANALYSES. 

Experience  in  cutting  through  glacial  moraines  for  rail- 
ways or  in  driving  levels  for  mining  operations  does  not 
qualify  a  man  for  exploration  of  a  Babylonian  or  prehistoric 
mound.  Human  occupations  have  left  upon  the  sand  and 
clay  evidences  which,  although  so  slight  as  to  be  unnoticed 
by  the  casual  observer,  are  like  an  open  book  to  him  who 
patiently  acquires  a  knowledge  of  the  meaning  of  the  dis- 
placements, discolorations,  and  enclosed  fragments.  Flowing 
water,  like  sand  and  clay  strata,  bears  evidences  of  its  previous 
history  no  less  intelligible  to  him  who  has  the  key  to  the 
cipher  and  who  adds  to  the  keen  eye  of  the  detective  and 
ready  wit  of  the  interpreter  the  sound  judgment  of  the  engi- 
neer. Reasoning  upon  insufficient  premises  will  as  often 
fail  in  the  one  case  as  in  the  other,  while  lucky  guesses  fre- 
quently encourage  superficiality  in  bo^h. 

After  the  analyst  has  entered  on  the  blank  (page  141)  the 
six  to  ten  records  needed  for  a  ground-water,  or  the  fifteen 
to  twenty  for  a  surface-water;  after  the  columns  headed 
Bacteria,  Diatoms,  Algae,  etc.,  have  been  filled  in,  there  still 
remains  the  summing  up  of  the  case  by  the  judge.  The 
correct  interpretation  of  results  means  a  knowledge  of 
the    source,     geological     horizon,     surroundings,     probable 


WATER:      THE    INTERPRETATION    OE    ANALYSES.  85 

changes,  and  the  significance  of  each  item  in  this  particular 
case.  Each  class  of  water  has  its  own  characteristics.  The 
presence,  in  quantity,  of  any  given  element  is  interpreted 
according  to  the  kind  of  water  under  consideration.  Spring- 
water  is,  of  course,  colorless;  lake-water  of  equal  safety  is 
probably  colored.  Spring-water  must  be,  as  a  rule,  free  from 
ammonia;  lake-water  may  at  times  contain  considerable 
amounts  without  detracting  from  its  good  character. 

Classification  of  Waters.  —  To  facilitate  examination, 
therefore,  waters  may  be  divided  into  three  classes:  first, 
cistern,  brook,  pond,  and  river  water — so-called  surface- 
zvater;  second,  spring  and  deep-well  water;  and  third,  shal- 
low wells  and  sewage  effluents. 

Water  of  the  last  tw^o  classes  has  been  for  greater  or  less 
periods  of  time  in  contact  with  rock  and  filtered  through 
sand,  hence  is  designated  as  ground-zvater. 

A  few  examples  taken  from  the  different  kinds  of  water 
showing  the  varying  conditions  to  which  they  are  subjected 
may  serve  to  make  the  rules  of  interpretation  clearer. 

Surface-Waters. — When  rain-water  falls  on  slated  or 
shingled  roofs  and  is  conducted  into  cisterns,  it  carries  with 
it  W'hatever  deposits  lave  collected,  the  pollen  of  forest-trees 
or  disease-germs  from  city  slums  many  miles  away;  from 
metal  roofs  it  takes  either  the  metal  itself  or  the  paint  rsed 
to  protect  the  surface.  In  all  cases,  lower  forms  of  animal 
life,  small  insects,  and  soot  from  chimneys  may  be  present. 
These  foreign  substances  should  be  at  once  filtered  out  with- 
out allowing  time  for  organic  decay,  unless  there  is  an  auto- 
matic device  for  wasting  the  first  washings  of  the  collecting 
surface.  There  are  still  substances  in  solution  which  would 
be  better  away;  therefore  the  water  is  allowed  to  stand 
quietly  in  order  that  the  changes  may  have  time  to  take 
place — to  ferment,  as  it  is  often  technically  expressed.     After 


86  AIR,    WATER,    AND    FOOD. 

this  season  of  purification  the  water  is  again  filtered  and 
stored  ready  for  use.  There  is  usually  color  and  a  little  am^ 
monia,  but  rarely  nitrates.  The  soluble  meta's,  if  once  pres- 
ent, still  remain.  It  goes  without  saying  that  all  such 
cisterns  must  be  absolutely  impervious  to  surface  drainage. 
For  lack  of  one  or  all  of  these  precautions,  cistern-water  has 
often  been  found  to  be  contaminated  from  cesspools,  from 
leaden  or  painted  roofs,  or  from  decaying  organic  mat  er. 

Brook-water. — The  rain  that  falls  on  mountain  slopes  of 
granitic  or  other  insoluble  rocks  washes  from  them  wha  ever 
loose  earth  may  have  fallen  there,  and  from  the  firmly  fixed 
lichens  the  small  insects  and  other  animal  forms  which  they 
harbor.  These  are  transported  in  brooks  to  the  lower  lands 
where  the  organisms  decay,  the  heavier  earthy  particles  fall- 
ing out  by  the  way. 

If  the  upland  rocks  and  soil  yield  a  portion  of  mineral 
salts  to  the  water,  it  may  come  out  clear  and  colorless  even  if 
it  has  not  penetrated  to  an  appreciable  depth. 

The  w^ater  from  these  forest  brooks,  after  remaining  im- 
pounded in  a  clean  lake  or  reservoir,  exposed  to  sunlight  and 
air,  often  becomes  the  safest  source  of  supply.  As  with  cis- 
terns, so  with  reservoirs,  filtration,  natural  or  artificial,  may 
take  place  previous  or  subsequent  to  storage,  or  both  before 
and  after. 

Lake  or  Mixed  Water. — Lakes  are  fed  by  springs  as  well 
as  by  brooks,  or  by  that  portion  of  rainfall  which  passes  a  few 
inches  below  the  surface,  and  is  filtered  before  reaching  the 
main  body.  If  the  banks  are  sandy  and  uninhabited,  the 
water  will  show  good  eft'ects  from  this  filtration;  but  if  the 
seepage-water  comes  from  a  settled  country,  it  w^ill  bring 
either  ammonia  or  nitrates.  The  analysis  will  quickly  show 
this  if  the  water  sample  can  be  taken  1)efor2  it  has  mixed 
3/vith  that   bearing  the   spores   of  plants   which   are   fed   by 


water:  tjie  ixterpretatiox  of  analyses.         Sy 

nitrates.     Often   the   very  presence   of  these  plants  furnishes- 
the  proof  sought. 

River-ivaters. — A  large  stream,  especially  a  muddy  one, 
may  receive  the  drainage  of  half  a  dozen  cities  a  hundred  miles 
distant  and  yet  not  give  conclusive  evidence  of  dangerous 
contamination,  while  a  small  river  with  a  rapid  current  may 
become  unsafe  from  the  presence  of  a  few  villages  a  dozen 
miles  away. 

Northeastern  America  is  so  well  supplied  with  uninhab- 
ited high  lands  for  collecting-grounds,  and  with  basins  in  the 
glacial  drift  for  storage  in  natural  or  artificial  lakes,  that  very 
few  rivers  need  to  be  used  after  they  have  become  polluted. 
The  Merrimac  and  the  Hudson  are,  however,  so  used.  In 
other  parts  of  the  country  the  use  of  rivers  is  an  increasing 
necessity,  requiring  municipal  filter  plants. 

From  every  point  of  view  organic  matter  should  be  kept 
as  far  as  possible  out  of  running  streams  which  mav  at  any 
time  be  needed  for  public  supplies,  or  the  natural  purifica- 
tion by  algae  should  precede  the  final  filtration  and  storage. 
It  is  quite  probable  that  this  double  treatment  may  be  more 
frequently  required  as  unpolluted  w^ater  becomes  more 
scarce. 

What  the  method  of  filtration  shall  be  depends  upon  the 
character  of  the  water,  whether  clear  or  turbid  with  clay, 
whether  certainly  polluted  or  only  with  a  remote  possibility 
of  contamination.  Each  problem  must  be  studied  by  itself 
without  prejudice  in  favor  of  any  one  method.  It  is  the  re- 
sult which  must  be  kept  in  mind,  namely,  the  furnishing  of 
safe  and  acceptable  water  to  the  community. 

Effect  of  the  Storage  of  Siirface-zuater. — In  interpreting 
his  results,  the  analyst  should  take  into  account  the  intiuence 
which  the  keeping  of  water  in  basins  has  upon  its  character. 
Storage  of  surface-water  is  of  utmcst  importance  in  all  cases. 


gg  AIR,    WATER,    AND    FOOD. 

of  doubt.  Most  disease-germs  find  such  water  an  unfavor- 
able medium  for  prolonged  life,  since  exposure  to  sunlight 
soon  destroys  the  darkness-loving  bacteria,  and  a  certain 
sterilizing  efYect  results  from  the  growth  of  green  alg^e,  so 
that  water  considerably  polluted  becomes  purified  if  given 
time  for  the  various  agents  to  do  their  work;  but  time  is 
essential. 

Odors. — For  surface-waters  one  of  the  links  in  the  chain 
of  evidence  is  found  in  the  odor,  cold  and  hot,  which  to  the 
trained  and  sensitive  nose  often  gives  convincing  testimony. 
A  musty  odor,  unmistakably  different  from  a  mouldy  vege- 
table smell,  betrays  sewage  contamination  even  when  the 
chemical  analysis  might  not  be  convincing.  This  odor  is  not 
always  taken  out  by  filtration,  neither  is  that  of  certain  or- 
ganisms growing  in  stored  water,  notably  Anahcena  and 
S\niira.  A  study  of  these  organisms  is  invaluable  to  the 
routine  observer  who  watches  the  seasonal  and  annual 
changes  in  his  reservoir. 

Turbidity  and  Sediment. — The  determination  of  turbid- 
ity and  sediment,  added  to  the  odor,  tells  much  to  the  expert, 
but  very  little  to  the  inexperienced  student.  Turbidity  may- 
be due  to  drainage  contamination,  to  growth  of  bacteria,  to 
clay,  to  iron,  to  swarms  of  micro-organisms.  Sediment  may 
be  sand,  zooglea,  fragments  of  plants  or  animals,  or  ferric 
oxide. 

Filtration. — The  subject  of  filtration  has  been  so  exten- 
sively treated  elsewhere  that  the  student  is  referred  to  the 
bibliography  on  page  263.  There  are  cases  in  which  it  is 
preferable  to  run  the  risk  of  too  much  alum  in  the  drinking- 
water,  and  too  much  sulphuric  acid  in  boiler  feed-water, 
rather  than  of  too  many  micro-organisms  with  the  accom- 
panying organic  matter. 

It  will  have  been  noticed  that  the  ideal  natural  w^ater  is 


water:    the  interpretation  of  analyses.        89 

that  which  has  been  earth-fiUered,  and  thus  all  suspended 
matter,  including  microbes,  has  been  removed.  This  sup- 
poses that  sufficient  time  has  elapsed  so  that  all  decomposing 
organic  matter  has  been  destroyed.  Man  tries  to  imitate 
nature's  processes,  but  expects  to  accomplish  it  in  moments 
instead  of  months. 

The  era  of  house-filters,  those  admirable  culture-grounds 
for  bacteria,  is  happily  nearly  past.  Taxpayers  are  becoming 
convinced  that  a  good  original  water-supply  in  competent 
hands  is  worth  paying  for.  Where  straining  only  is  needed, 
a  fiannel  bag  washed  daily  is  as  efficient  as  any  faucet-filter. 
If  the  latter  takes  out  color  as  well,  it  should  be  closely 
Avatched.  Water  should  not  be  first  boiled  and  then  filtered, 
but  first  filtered  and  then  boiled. 

Summary. — Surface-zvatcr. — In  general  it  may  be  said 
that  the  waters  of  the  first  class  found  in  New  England  are 
generally  more  or  less  colored,  and  contain  more  or  less  sus- 
pended organic  life  and  its  debris,  which  often  impart  a  de- 
cided odor  to  the  water.  These  waters,  draining  for  the  most 
part  wooded  and  sparsely  populated  regions,  are  low  in  free 
ammonia,  nitrates,  and  nitrites;  low,  also,  in  mineral  salts, 
and  with  only  a  slight  excess  of  chlorine  over  the  normal. 
They  are  usually  high  in  organic  matter  and  albuminoid  am- 
monia even  when  entirely  free  from  pollution. 

In  other  parts  of  the  United  States  surface-waters  may  be 
low  in  color,  but  with  much  suspended  clay  and  silt,  and  may 
hold  in  solution  notable  quantities  of  mineral  salts.  The 
latter  aid  greatly  in  the  clarification  by  artificial  filtration, 
which  is  so  often  rendered  necessary  by  the  excessive  turbid- 
ity even  if  not  by  sewage  contamination. 

In  Table  IV,  page  239,  will  be  found  examples  showing 
at  a  glance  how  profoundly  the  character  of  a  water  is  affected 
by  the  geological  horizon,  whether  its  source  is  in  the  glacial 


go  AIR,    WATER,    AND    FOOD. 

drift  of  the  Appalachian  region,  or  in  the  Umestone  of  the 
Hudson  River  Valley,  or  in  the  saline  deposits  of  the  sub- 
sided areas. 

Deep  Wells  and  Springs. — The  waters  of  the  second  class 
are  derived  from  the  depths  of  the  earth,  far  below  any  pos- 
sible surface  contamination,  and  have  long  been  imprisoned 
in  the  dark  and  cold,  and  often  subjected  to  great  pressure- 
The  influence  of  pressure  on  organisms  has  not  been  entirely 
worked  out,  but  from  what  is  known  it  is  probably  very  un- 
favorable to  the  life  of  the  lower  organisms.  The  results  of 
many  bacterial  examinations  have  been  vitiated  by  the  difft- 
culty  of  securing  a  sample  from  great  depths  without  con- 
tamination by  surface  exposure — pipes  open  to  the  air  har- 
boring many  forms  of  life. 

Deep  wells,  700  feet  and  more,  are  not  likely  to  be  dan- 
gerous. They  may  often  contain  ammonia  from  prehistoric 
coal-fields  or  tertiary  deposits,  but  rarely  nitrates.  This  is 
accounted  for  by  the  fact  that  ''  the  result  of  the  changes  of 
the  nitrogenous  organic  substances  which  fall  into  the  earth 
is,  without  doubt,  frequently  the  formation  of  gaseous  nitro- 
gen." Also,  that  ''  salts  of  nitric  acid  on  penetrating  into 
the  depths  of  the  earth  give  up  their  oxygen."  * 

Owing  to  their  long  sojourn  in  the  depths  of  the  earth, 
these  waters  are  higher  in  mineral  substances  than  surface- 
waters.  Since  their  origin  is  unknown,  the  chlorine  cannot 
be  correctly  gauged,  especially  as  there  are  saline  waters  deep 
down  in  rock  cavities  in  all  parts  of  the  world. 

It  is  usually  believed  that  these  deep  wells  furnish  a  safe, 
palatable  water  when  the  kind  and  amount  of  mineral  matter 
is  not  objectionable. 

Shallow  Wells. — It  is  not  to  be  wondered  at  that  waters 

.  •,  ^  *  Mendel^eff :  "Chemistry,"  p.  223. 


water:    the  interpretation  of  analyses.        91 

of  the  third  class — ground-water,  taken  from  just  beneath 
the  surface  layers  of  the  soil — should  contain  many  sub- 
stances foreign  to  the  waters  about  them  as  well  as  to  those 
at  greater  depths.  The  shallow  wells,  which  are  practically 
more  or  less  diluted  sewage  effluents,  present  the  greatest 
variety.  They  may  be  clear  and  colorless  and  show  as  great 
organic  purity  as  the  best  mountain  spring.  In  other  cases, 
the  overworked  filter  permits  the  passage  of  organisms  and 
undecomposed  material.  In  either  case  there  will  be  found 
those  compounds  which,  being  soluble  and  stable,  are  car- 
ried with  the  water  as  signs  to  be  read  by  him  who  knows  the 
language.  A  complete  history  of  each  specimen  of  this  class 
of  ground-water  is  desirable,  and  with  sufficient  patience 
and  care  it  may  be  obtained  with  reasonable  accuracy,  if  the 
principles  governing  the  circulation  of  water  and  the  changes 
of  the  organic  matter  it  carries  be  kept  well  in.  mind. 

It  is  certain  at  once  that  absence  of  color,  of  organic  mat- 
ter in  any  form,  and  of  odor  should  be  insisted  upon,  for 
ground-water  is  filtered  water  and  the  filter  should  be  doing 
its  work. 

A  modicum  of  geological  knowledge  is  essential,  as  the 
presence  of  shaly  or  slaty  rock  will  permit  the  passage  into 
underground  water  of  surface  drainage  with  less  purification 
than  will  a  granite  or  sandstone  region.  A  clayey  soil  is  a  less 
efficient  filter  than  a  sandy  loam  and  permits  the  pollution 
to  travel  farther. 

Nitrogen  in  Well-zvater — It  may  be  taken  as  an  axiom 
that  the  only  form  of  nitrogen  permissible  in  a  good  ground- 
water is  that  of  nitrates,  a  fully  oxidized  or  mineralized  food 
for  green  plants.  If  nitrites  are  also  present,  a  source  of 
pollution  Is  at  hand,  for,  as  has  been  said,  nitrites  indicate 
either  a  stage  of  oxidation  not  completed  or  one  of  reduction 
from  nitrates  in  the  presence  of  organic  matter.     If  free  am- 


92  AIR,    WATER,    AND    FOOD. 

monia  be  present,  it  is  safe  to  say  that  the  source  is  not  only- 
near  but  in  actual  contact,  since  but  a  few  hours'  time  is 
needed  to  oxidize  the  ammonia  in  any  soil  not  waterlogged. 
It  may  also  be  pretty  safe  to  assume  that  bacteria  are  present, 
since  ammonia  is  the  first  stage  of  that  decomposition  which 
they  accompany.  It  is  the  part  of  prudence,  therefore,  to 
avoid  any  water  which  contains  both  free  ammonia  and 
nitrites  above  .200  or  .300  parts  per  million  of  the  first,  and 
.020  or  .030  of  the  second. 

The  absorption  of  nitrogen  by  plants  is  rarely  complete, 
so  that  it  usually  appears  in  far  larger  quantities  in  contami- 
nated ground-waters  than  could  be  obtained  from  purified 
rain-w^ater.  The  leaching  cesspool  discharges  its  liquid  con- 
tents below  the  zone  of  green-plant  life;  fertilized  soil  also 
yields  a  portion  of  its  food  value  to  the  lower  layers.  A 
small  portion  of  the  nitrogen  of  vegetable  origin  may  appear 
as  nitrates,  but  only  as  a  derivative  of  soil  rich  in  humus  is  it 
likely  to  play  any  considerable  part.  In  eastern  America 
nitrates  above  0.5  parts  per  million  would  arouse  suspicion, 
and  above  5  parts  would  in  most  cases  prove  prev^ious  pollu- 
tion. 

It  is  evident  that  in  the  use  of  nitrogen  as  an  indicator  of 
the  conditions  of  a  water  we  are  limited,  by  the  changeful 
character  of  the  compounds,  to  certain  not-to-be-mistaken 
amounts,  and  that  in  the  majority  of  cases  the  evidence  given 
is  not  decisive. 

Chlorine  in  Well-water. — Fortunately  there  is  another  ele- 
ment not  so  eagerly  sought  for  by  plants  and  not  liable  to  so 
many  transformations.  Thanks  to  the  ^reat  solubility  of  its 
common  compounds  and  to  their  stability,  chlorine,  once  a 
constituent  of  a  given  body  of  water,  is  not  extracted  there- 
from and  remains  as  a  telltale  to  reveal  the  past  history  of  a 
stream  or  spring.     If  a  man  is  judged  by  the  company  he 


\ 


H^ 


/  ;>  «^;l...^  ^  ^,. 


\ 


n-^^yTt, 


■■'iri 


^6 


-x/y 


OVA  ^ 

4-   - 


ilii>A 


^j^M.M:-i^'':^^ 


/■^: 


S-LVTE  BOARD  OF  HEALTH 

MAP  OF  THE 

The  lines  represent  norma!  chlorine. 

STATE  OF  MASSi\CHUSETTS.  '^^'jzzr^  •""-"''  "°'°" 

SHOWING 


NORMAL   CHLORINE. 


^^^^/^    . 


WATER:     THE    INTERPRETATION    OF    ANALYSES.  93 

keeps,  much  more  a  water-supply.  From  sewage  all  the 
nitrogen  may  be  removed  and  the  chlorine  still  remain. 

But  in  order  to  use  this  information  with  any  degree  of 
certainty  the  normal  chlorine  of  the  locality  must  be  known. 
If  a  map  showing  isochlors  has  been  made  of  the  region  or 
State,  and  if  there  are  no  geological  deposits  to  interfere,  this 
is  easy;  but  if  the  chemist  or  engineer  has  an  unknown  coun- 
try to  report  upon,  it  will  be  necessary  to  examine  the  local 
conditions  and  to  choose  six,  eight,  or  ten  samples  of  prob- 
able freedom  from  contamination  and  to  test  them  for  com- 
parison. The  sources  of  the  excess  of  chlorine  over  the 
normal  are  usually  the  sink-drain  with  its  burden  of  salted 
water  from  domestic  operations;  the  house-drain,  with  its 
chlorine-containing  excreta;  and  the  stable-drain,  with  a 
slight  chlorine  content  in  comparison  with  the  other  two. 

Mineral  Substances. — Since  water  *s  a  universal  solvent, 
it  is  not  surprising  to  find  considerable  amounts  of  mineral 
matter  in  the  two  columns  ''  Total  Solid  Residue  on  Evapo- 
ration "  and  "  Hardness."  How  much  calcium  sulphate  or 
magnesium  chloride  or  other  soluble  mineral  is  allowable  in 
a  potable  water  is  for  the  physician  rather  than  the  chemist 
to  say.  As  has  been  said,  the  human  system  possesses  great 
adaptability,  not  only  for  different  foods,  but  for  mineral  sub- 
stances water-carried.  Not  so  the  steam-boiler  or  the  laundry- 
tub,  which  reacts  very  sensitively  and  afifects  the  pockets 
of  the  consumers.  In  a  region  of  soft  water,  high  solids 
with  chlorine  and  nitrates  indicate  sewage  pollution. 
Silica  is  much  more  commonly  present  even  in  surface- 
waters  than  is  often  supposed.  What  its  effect  may  be  is 
unknown.  Iron  is  not  uncommonly  found  in  combination 
with  organic  matter  in  either  surface  or  imperfectly  filtered 
w^aters  in  contact  w^ith  soils  poor  in  calcium  salts.  It  is  fre- 
quently  accompanied    by    free    ammonia,    which    causes   an 


water:    the  interpretation  of  analyses.        93 

keeps,  much  more  a  water-supply.  From  sewage  all  the 
nitrogen  may  be  removed  and  the  chlorine  still  remain. 

But  in  order  to  use  this  information  with  any  degree  of 
certainty  the  normal  chlorine  of  the  locality  must  be  known. 
If  a  map  showing  isochlors  has  been  made  of  the  region  or 
State,  and  if  there  are  no  geological  deposits  to  interfere,  this 
is  easy;  but  if  the  chemist  or  engineer  has  an  unknown  coun- 
try to  report  upon,  it  will  be  necessary  to  examine  the  local 
conditions  and  to  choose  six,  eight,  or  ten  samples  of  prob- 
able freedom  from  contamination  and  to  test  them  for  com- 
parison. The  sources  of  the  excess  of  chlorine  over  the 
normal  are  usually  the  sink-drain  with  its  burden  of  salted 
water  from  domestic  operations;  the  house-drain,  with  its 
chlorine-containing  excreta;  and  the  stable-drain,  with  a 
slight  chlorine  content  in  comparison  with  the  other  two. 

Mineral  Substances. — Since  water  *s  a  universal  solvent, 
it  is  not  surprising  to  find  considerable  amounts  of  mineral 
matter  in  the  two  columns  ''  Total  Solid  Residue  on  Evapo- 
ration "  and  "  Hardness."  How  much  calcium  sulphate  or 
magnesium  chloride  or  other  soluble  mineral  is  allowable  in 
a  potable  water  is  for  the  physician  rather  than  the  chemist 
to  say.  As  has  been  said,  the  human  system  possesses  great 
adaptability,  not  only  for  difTerent  foods,  but  for  mineral  sub- 
stances water-carried.  Not  so  the  steam-boiler  or  the  laundry- 
tub,  which  reacts  very  sensitively  and  alYects  the  pockets 
of  the  consumers.  In  a  region  of  soft  water,  high  solids 
with  chlorine  and  nitrates  indicate  sewage  pollution. 
Silica  is  much  more  commonly  present  even  in  surface- 
waters  than  is  often  supposed.  What  its  effect  may  be  is 
unknown.  Iron  is  not  uncommonly  found  in  combination 
with  organic  matter  in  either  surface  or  imperfectly  filtered 
waters  in  contact  with  soils  poor  in  calcium  salts.  It  is  fre- 
quently  accompanied    by    free    ammonia,    which    causes   an 


94  AIR,    WATER,    AND   FOOD. 

abundant  growth  of  Cniiothrix.  It  is  also  present  in  deep 
wells  in  the  form  of  carbonate,  which  precipitates  on  exposure 
to  warm  air.  ^ 

In  a  considerable  number  of  cases  of  public  water-supply 
there  is  a  mixture  of  surface  and  ground  water  which  com- 
plicates the  verdict,  requiring  a  most  delicate  balancing  of 
probabilities.  The  mineral  contents  often  aid  in  this  deci- 
sion. \\>11- waters,  too,  are  often  exposed  to  surface-wash 
because  of  poor  protection  at  the  mouth.  Cyclops  or  other 
surface-water  organisms  often  indicate  this. 

irafcr-pipcs. — After  all,  if  the  pipes  conveying  the  water 
are  of  lead  or  brass,  an  additional  danger  appears.  Gen- 
erally speaking,  the  purer  the  water  the  greater  the  risk. 
No  common  metal  seems  to  withstand  the  action  of  soft 
water;  six  to  eight  years  being  the  average  age  of  galvanized 
pipe,  and  eight  to  ten  of  iron  pipe.  It  would  seem  as  if 
wooden  pipe  must  come  into  greater  use  until  some  kind 
of  glass  is  in\'ented  which  will  withstand  this  corrosive 
action  and  yet  admit  of  plumber's  connections. 

Value  of  Tests.— It  is  often  asked  if  some  tests  cannot  be 
made  by  the  ordinary  person  of  average  intelligence  which 
Avill  enable  him  to  tell  the  quality  of  a  water  as  well  as  the 
expert  to  whom  he  pays  ten  or  twenty  dollars  for  an  opinion. 
A  careful  perusal  of  the  preceding  pages  will  have  answered 
the  question  in  the  negative.  There  is  no  assay  of  water  as 
there  is  of  gold  and  silver.  Not  one  but  ten  or  twenty  tests 
must  be  made.  Not  only  must  the  tests  be  made  with  the 
utmost  care  and  cleanlines-s  of  person,  utensils,  and  room,  but 
the  results  must  be  studied  in  the  light  of  other  experience 
and  other  knowledge;  geological  and  biological,  and  after 
all  this  is  done  there  is  an  array  of  circumstantial  evidence 
which  must  be  carefully  weighed  by  one  whose  judgment  and 
experience  ena'bk  him  to  read  clearly  where  another  might 


WATER:     THK    INTERPRETATION    OF    ANALYSES.  95 

see  nothing.  The  value  of  a  water-analysis  is  in  direct  pro- 
portion to  the  knowledge  and  experience  of  the  one  who 
interprets  it.  Clinical  skill  in  addition  to  theoretical  knowl- 
edge is  required  to  interpret  the  figures  obtained  in  the  course 
of  a  water-analysis,  as  in  the  symptoms  of  a  disease:  and  the 
analogy  goes  still  further,  for  as  some  diseases  are  clearly 
defined,  others  are  so  complicated  that  only  those  who  have 
had  long  experience  can  outline  a  safe  course  of  treatment; 
so  some  waters  bear  the  marks  of  their  character  so  plainly 
as  not  to  admit  of  mistake,  while  others  require  most  careful 
study.  For  these  reasons  the  value  of  water-analysis  should 
not  be  decried  because  the  fears  aroused  by  reports  given  by 
tmskilled  analysts  prove  groundless,  any  more  than  the  prac- 
tice of  medicine  should  be  discarded  because  inexperienced 
men  make  mistakes. 

Is  the  water  in  any  given  case  safe  for  drinking?  To  an- 
swer this  question  there  is  needed  a  knowledge  wider  than  a 
chemist's  of  the  relation  of  decaying  organic  matter  and  of 
the  germ-carrying  power  of  water  to  outbreaks  of  disease. 
There  must  be  added  the  knowledge  of  the  biologist,  the  en- 
gineer, and  the  sanitarian. 


CHAPTER  VII. 

ANALYTICAL    METHODS.* 

General  Statements. — Water-analysis  cannot  be  carried  on 
in  an  ordinary  laboratory.  In  order  to  obtain  satisfactory 
results  it  is  necessary  to  have  a  room  set  apart  for  the  pur- 
pose, and  to  exclude  rigidly  all  operations  which  tend  to  the 
production  of  fumes  or  dust.  Where  such  minute  traces  of 
substances  are  dealt  with  as  in  water-analysis,  too  much  care 
cannot  be  taken  to  insure  the  absolute  cleanliness  of  the  ap 
paratus  and  the  surroundings.  It  is  desirable  that  the  room 
be  well  lighted,  and  if  possible  the  windows  should  face 
toward  the  north. 

The  methods  for  the  examination  of  water  which  are  de- 
scribed in  this  chapter  by  no  means  comprise  all  that  are  in 
use.  The  directions  are  given  for  the  use  of  students  in  our 
own  laboratory  under  the  conditions  obtaining,  i.e.,  of  large 
classes  and  of  several  courses  of  study,  with  especial  reference 
to  educational  rather  than  purely  technical  needs,  and  in  some 
cases,  no  doubt,  the  traditions  of  thirty  years  may  have  unduly 
persisted.  The  methods  have  been  so  selected  as  to  intro- 
duce a  variety  of  apparatus  and  to  illustrate  principles.  They 
have  also  been  subjected  to  a  thorough  test  in  meeting  the 
demands  of  practical  work. 

Collection  of  Samples. — For  the  collection  of  w^ater  sam- 
ples, glass-stoppered  bottles  of  about  a  gallon  capacity  are 
best.  Those  used  in  this  laboratory  are  of  white  glass,  fifteen 
inches  high  to  the  top  of  the  stopper,  five  and  a  half  inches 

*  See  Report  of  Committee  on  Standard  Methods  of  Water-analysis,  Jour,  of 
Infectious  Diseases,  Supplement  No.  I,  May,  1905. 

96 


water:   analytical  methods.  97 

in  diameter,  and  weigh  about  three  pounds.  They  have  flat,, 
mushroom  stoppers,  on  which  is  engraved  a  number  to  corre- 
spond with  that  on  the  bottle.  The  bottles,  before  being- 
sent  out,  are  thoroughly  cleaned  with  potassium  bichromate 
and  sulphuric  acid,  washed  with  distilled  water  and  dried.  If 
glass-stoppered  bottles  are  not  at  hand,  new  demijohns  fitted 
with  nezu  corks  may  be  used.  A  glass  bottle  or  a  demijohn 
is  much  to  be  preferred  to  an  earthenware  jug,  because,  if  for 
no  other  reason,  it  is  so  much  easier  to  be  sure  that  the  interior 
is  clean.  It  should  always  be  borne  in  mind  that  in  water- 
analysis  the  question  is  one  of  very  minute  quantities  of  mate- 
rial, and  that  the  methods  to  be  employed  are  extremely 
delicate.  Hence,  in  the  case  of  many  waters,  careless  hand- 
ling of  the  sample  would  contaminate  the  water  to  a  suf^cient 
extent  to  render  valueless  the  results  obtained  in  the  labora- 
tory. In  collecting  samples,  the  following  directions  should 
be  closely  followed:  * 

Directions  for  Collecting  Samples  for  Analysis — From 
a  Water-tap. — Let  the  water  run  freely  from  the  tap  for  a 
few  minutes  'before  collecting  the  sample.  Then  place  the 
bottle  directly  under  the  tap  and  rinse  it  out  with  the  water 
three  times,  pouring  out  the  water  completely  each  time. 
Place  it  again  under  the  tap;  fill  it  to  overflowing  and  pour 
out  a  small  quantity  so  that  there  shall  be  left  an  air-space 
under  the  stopper  of  about  an  inch.  Rinse  ofT  the  stopoer 
with  flowing  water;  put  it  into  the  bottle  while  still  wet  and 
secure  it  by  tying  over  it  a  clean  piece  of  cotton  cloth.  Seal 
the  ends  of  the  string  on  the  top  of  the  stopper.  Under  no 
circumstances  touch  the  inside  of  the  neck  of  the  bottle  or 
the  stem  of  the  stopper  with  the  hand,  or  wipe  it  with  a 
cloth. 

From  a  Stream,  Pond,  or  Reservoir. — Rinse  the  bottle  and 


*  Ann.  Rep.  Mass.  State  Board  of  Health,  1890,  p.  520. 


q8  air,  water,  and  food. 

stopper  with  the  water,  if  this  can  be  done  without  stirring 
up  the  sediment  on  the  bottom.  Then  sink  the  bottle,  with 
the  stopper  in  place,  entirely  beneath  the  surface  of  the  water 
and  take  out  the  stopper  at  a  distance  of  twelve  inches -or 
more  below  the  surface.  When  the  bottle  is  fu  1  replace  the, 
stopper,  below  the  surface  if  possible,  and  secure  it  as  directed 
above.  It  will  be  found  convenient,  in  taking,  samples  in 
this  way,  to  have  the  bottle  weighted  so  that  it  will  sink  be- 
low the  surface,  and  to  remove  the  stopper  by  a  cord.  It  is 
important  that  the  sample  should  be  obtained  free  from  the 
sediment  at  the  bottom  of  a  stream  and  from  the  scum  on 
the  surface.  If  a  stream  should  not  be  deep  enough  to  admit 
of  this  method  of  taking  a  sample,  dip  up  the  water  with  an 
absolutely  clean  vessel  and  pour  it  into  the  bottle  after  the 
latter  has  been  rinsed. 

The  sample  of  water  should  be  collected  immediately  be- 
fore shipping  by  express,  so  that  as  little  time  as  possible 
shall  interv^etie  between  the  collection  of  the  sample  and  its 
examination.  All  possible  information  should  be  furnished 
concerning  the  source  of  the  water  and  of  possible  sources  of 
contamination.  For  example,  in  the  case  of  a  well,  the  prox- 
imity of  dwellings,  cesspools,  or  drains  should  be  recorded, 
and  the  character  and  slope  of  the  soil,  whether  toward  or 
away  from  the  well,  should  be  noted.  In  the  case  of  a  sur- 
face-water, mention  any  abnormal  or  unusual  conditions;  as, 
for  instance,  if  the  streams  or  ponds  are  swollen  by  recent 
heavy  rains,  or  are  unusually  low  in  consequence  of  prolonged 
•drought,  or  if  there  be  a  great  deal  of  vegetable  growth  in  or 
on  the  surface  of  the  water.  Record,  in  short,  any  circum- 
stantial evidence  which  by  any  possibility  may  aid  in  the  final 
judgment. 

The  question  of  proper  collection  of  samples  is  an  impor- 
tant one,  and  the  chemist  is  perfectly  justified  in  refusing  to 


water:   analytical  methods.  99 

give  an  opinion  in  regard  to  the  purity  of  a  water  which  he 
has  not  himself  collected.  The  ignorance  and  carelessness 
shown  by  people  who  send  samples  for  analysis  are  often- 
times quite  amusing.  Samples  have  been  received  at  this 
laboratory  in  almost  every  kind  of  container  imaginable,  from 
an  imperfectly  rinsed  whisky-bottle  to  a  discarded  syrup-jug, 
with  about  an  inch  of  maple  sugar  in  the  bottom.  One  sam- 
ple was  sent  all  the  way  from  Georgia  in  a  stone  jug  with  a 
corn-cob  inserted  for  a  stopper.  Others  are  received  with 
the  stopper  carefully  (?)  protected  by  a  mass  of  sealing-wax 
or  candle-grease.  A  favorite  way  is  to  send  the  sample  in  a 
fruit-jar  packed  in  sawdust  or  straw.  Opinions  evidently 
differ  greatly,  too,  in  regard  to  the  size  of  sample  that  is 
needed.  It  is  no  uncommon  occurrence  to  have  a  person 
■come  into  the  laboratory  with  the  remark,  ''  Here  is  a  sample 
of  water  that  I  want  analyzed,"  supplemented  by  the  produc- 
tion from  a  coat-pocket  of  a  homoeopathic  vial  or  a  sample 
of  half  a  pint  or  so  of  water.  Of  course,  in  cases  like  these 
practically  nothing  can  be  done. 

Preparation  of  the  Sample  for  Analysis. — Since  changes 
in  the  composition  of  a  contaminated  water  are  constantly 
going  on,  the  analysis  of  the  sample  should  be  begun  without 
delay.  The  bottle  is  held  under  the  tap.  and  the  neck  and 
stopper  are  washed  free  from  adhering  dust.  The  stopper  is 
rinsed  off  with  some  of  the  water  from  the  bottle.  Qualita- 
tive tests  should  be  made  for  ammonia,  nitrites  and  chlorine. 
With  waters  containing  much  suspended  matter,  and  in  the 
case  of  surface-w^aters  in  which  it  is  desired  to  distinguish 
between  the  organic  matter  in  solution  and  that  in  suspen- 
sion, a  portion  of  the  water  should  be  filtered.  In  most 
cases  the  suspended  matter  can  be  removed  by  filtration 
through  paper.  For  this  purpose  only  the  best  Swedish 
tfilter-paper  should  be  used,  and  the  filters  should  be  first 


lOO 


AIR,    WATER,    AND    FOOD. 


thoroughly  washed  with  ammonia-free  water.  With  some 
waters  containing  very  finely  divided  clay  in  suspension,  fil- 
tration through  paper  will  not  be  satisfactory,  and  the  sample 
must  be  filtered  by  suction  through  a  cylinder  of  ung'azed 
porcelain,  such  as  an  ordinary  Chamberland-Pasteur  fil  er- 
tube.  In  the  filtered  water  it  is  customary  to  determine  the 
dissolved  solids,  the  albuminoid  ammonia,  or  the  organic 
nitrogen,  and  the  color. 

Determination  of  Free   and   Albuminoid  Ammonia. — 
Apparatus* — The  apparatus  used  for    the   determination    of 

ammonia  is  that  shown 


in    Fig.  8 


It  consists- 
of  a  round-bottomed 
flask  of  900  c.c.  capaci- 
ty, with  square  shoul- 
ders and  a  narrow  neck 
five  inches  long,  and  an 
ordinary  Liebig  con- 
denser fitted  with  aa 
inner  tube  of  block  tin,, 
^/i6  of  an  inch  in  diame- 
ter. The  flask  is  closed 
by  a  cork  carrying  a 
glass  tube  bent  nearly  at 
right  angles,  which 
Slips  for  some  distance 
within  the  tin  tube  cf 
the  condenser.  A  tight 
joint  is  made  by  means 
of  a  large  cork,  which 
is  shown  in  section  in 
Fig.  9.  The  large  cork 
serves  the  double  purpose  of  making  a  tight  joint  with  the 


ScaleJHin.=  lfooi. 
Fig.  8. — Apparatus  for  Ammonia  Dis- 
tillation, 


*  A.  H.  Gill  :  /.  Ana/,  and  App.  Chem.,  6  {iSgz),  669. 


WATER:     ANALYTICAL    METHODS. 


lOI 


condenser  and  also  as  a  convenient  means  for  handling  the 
small  glass  tube.  In  order  to  remove  fehe  cork  from  the  dis- 
tilling-flask,  the  glass  tube  carrying  it  is  simply  turned  to  one 
side,  using  the  large  cork  as  a  pivot.  The  flasks  are  heated 
with  the  free  flame  of  a  Bunsen  burner. 

New  flasks  are  treated  with  boiling  dilute  sulphuric  acid 
and  potassium  bichromate  before  they  are  used.  New  corks 
should  be  steamed  out  for  one  or  two  hours.  A  good,  sound 
cork  will  last  for  several  months  with  daily  use.     The  dis- 


CORK    JOINT 

FuU  Size 

Fig.  9. 

tillates  are  received  into  small  50-c.c.  flasks  and  poured  into 
Nessler  tubes  for  nesslerization.  The  Nessler  tubes  are  11 
inches  long  and  f-inch  internal  diameter,  the  50-c.c.  mark 
being  about  two  inches  from  the  top.  It  is  desirable  to  so 
arrange  the  apparatus  as  to  collect  the  distillates  directly  in 
the  Nessler  tubes  and  at  the  same  time  render  the  apparatus 
more  compact  by  having  several  condenser  tubes  run  through 
a  common  cooling  tank.  For  class  work,  however,  the  appa- 
ratus just  described  has  been  found  most  suitable. 

Directions. — Free  the  apparatus  from  ammonia  by  dis- 
tilling off  the  water  in  the  flask,  testing  each  50-c.c.  portion 
of  the  distillate  until  no  color  is  given  with  the  Nessler  re- 
agent.     When  the   distillate   is  free  from  ammonia,  pour  the 


I02  AIR,   WATER,   AND   FOOD. 

water  left  in  the  flasks  into  the  bottle  marked  "  Ammonia- 
free  residues." 

Shake  the  bottle  thoroughly  to  mix  the  sample.  For 
determining  the  ammonia  measure  out  in  a  calibrated  flask  a 
portion,  usually  500  c.c.,  the  amount  taken  depending  upon 
the  result  of  the  qualitative  test.  Pour  this  into  the  distilling- 
flask,  and  distil  over  three  portions  of  50  c.c.  each  into  Nessler 
tubes  or  into  the  graduated  flasks. 

In  dealing  with  sewage  or  sewage  efliuents,  which  are  very 
high  in  free  ammonia,  if  the  ammonia  were  collected  in  three 
portions,  so  much  would  distil  over  in  the  first  portion  that 
the  color  given  with  Nessler's  reagent  would  often  be  too  deep 
to  read  or  a  precipitate  might  form.  To  avoid  this  the  total 
distillate  of  150  to  175  c.c.  is  collected  in  a  200-c.c.  graduated 
flask,  made  up  to  the  mark,  thoroughly  mixed  by  pouring,  and 
then  50  c.c.  of  it  taken  for  nesslerization.  In  tins  way  the 
ammonia  is  distributed  more  evenly  in  the  distillate  and  the 
determination  is  not  sacrificed. 

Notes. — When  the  amount  of  ammonia  shown  by  the  quali- 
tative test  is  high — i.e.,  shows  a  color  equivalent  to  I.  c.c.  of  the 
standard  ammonia  solution — a  less  quantity  than  500  c.c.  should 
be  taken  for  the  distillation,  100  c.c.  or,  in  the  case  of  sewage, 
even  10  c.c.  being  diluted  to  500  c.c.  with  water  free  from 
ammonia.  Sewage  and  soils  may  be  distilled  with  steam  in 
the  apparatus  figured  on  page  106  under  the  Kjeldahl  pro- 
cess. 

After  the  free  ammonia  has  been  distilled  off,  allow  the 
contents  of  the  flask  to  cool  slightly;  then  add  40  c.c.  of  alka- 
line permanganate  through  a  funnel,  taking  care  that  none  of 
the  alkaline  soluion  touches  the  neck  of  the  flask,  and  proceed 
with  the  distillation  of  the  albuminoid  ammonia;  that  is  to 
say,  the  determination  of  the  nitrogen  of  the  undecomposed 
organic   matter.     With    colored   surface-waters   distil   off   five 


water:  analytical  methods.  1103- 

portions  of  50  c.c.  each;  with  waters  of  low  organic  .content 
three  or  four  portions  will  suffice.  ^H^^  ^ 

In  order  to  obtain  about  one  half  the  total  organic  nitrogen 
regulate  the  height  of  the  flame  so  that  the  time  of  distilling 
50  c.c.  shall  not  be  more  than  eight  and  not  less  than  five 
minutes. 

It  is  impossible  to  convert  all  of  the  organic  nitrogen  into- 
ammonia  by  boiling  with  alkaline  permanganate.  The  amount 
of  ammonia  which  is  thus  obtained  depends  not  only  upon  the 
character  of  the  substances,  but  also  upon  the  concentration 
of  the  solution  and  the  rate  of  boiling.  In  order  that  the 
albuminoid  ammonia  in  potable  waters  shall  bear  some  definite 
relation  to  the  total  organic  nitrogen,  it  is  necessary  that  these 
conditions  shall  be  duplicated  as  nearly  as  possible  in  different 
determinations;  that  is,  the  alkaline  permanganate  must  be 
added  to  a  definite  volume  of  the  water,  and  the  boiling  must 
be  carried  on  at  a  definite  rate.  Some  of  the  highly  colored 
surface-waters  give  up  their  nitrogen  very  slowly  by  this  treat- 
ment; polluted  waters,  on  the  other  hand,  yield  the  ammonia 
more  rapidly,  so  that  the  observation  of  the  relative  amounts 
found  in  the  successive  portions  is  of  the  utmost  importance 
in  forming  a  judgment. 

Have  the  Nessler  tubes  clean  and  thoroughly  rinsed  with 
ammonia-free  water.  Unless  permanent  standards  are  used 
prepare  standards  by  adding  to  Nessler  tubes  nearly  filled 
with  ammonia-free  water  varying  quantities  of  the  standard 
ammonium  chloride  solution;  for  instance,  o.i,  0.3,  0.5,  0.7, 
i.o,  1.3,  1.5,  2.0,  2.5,  4.0,  6.0  c.c.  The  standard  ammonium 
chloride  solution  contains  .00001  gram  N  in  one  cubic  centimeter. 

Mix  the  contents  of  the  tubes  by  rotating  them  between 
the  palms  of  the  hands  (never  shake  them  like  a  test-tube  or 
stir  them  with  a  rod),  allow  them  to  stand  for  two  or  three 
minutes,  and   add  i  c.c.  of  the  Nessler's  reagent  to  the  whole 


I04  AIR,    WATER,    AND   FOOD. 

set,  and  to  the  samples  to  be  tested,  as  rapidly  as  possible. 
At  the  end  of  ten  minutes  match  the  colors  and  record  the 
amount  of  ammonia. 

As  an  example  of  a  colored  surface-water  may  be  given 
the  following  results  from  distilling  500  c.c: 

Free  Ammonia.  Albuminoid  Ammonia. 

1st  50  c.c,     0.7  c.c.  1st  50  c.c,  4-5  c.c. 

2d    50  c.c,     0.3  c.c.  2d  50  c.c,  2.8  c.c. 

3d    50  c.c,     0.0  c.c  3d  50  c.c,  1.5  c.c. 

4th  50  c.c,  i.o  c.c 

5th  50  c.c,  0.5  CO. 


1.0  c.c  10.3  cc. 

In  this  case  the  free  ammonia  would  be  0.020  and  the 
albuminoid  ammonia  .206  parts  per  million. 

In  the  case  of  water  from  suspicious  wells  and  of  sewage 
effluents,  about  0.5  gram  of  freshly  ignited  sodium  carbonate 
should  be  added  before  distillation,  in  order  to  make  sure  that 
the  reaction  of  the  water  is  not  acid,  and  to  decompose  any 
urea  which  may  be  present.  This  will  not  be  necessary  with 
ordinary  surface-waters,  as  experience  has  shown  that  they 
almost  always  have  a  slight  alkaline  reaction. 

A  depth  of  color  given  by  6  c.c.  of  the  standard  ammonium 
chloride  with  the  Nessler  reagent  is  about  the  limit  of  satis- 
factory comparison  in  the  ii-inch  50  c.c.  tubes.  The  color 
.given  by  10  or  12  c.c.  of  the  standard  may  be  matched  in  the 
100  c.c.  tubes  with  a  depth  of  5  inches  and  a  diameter  of  ij 
inches. 

For  most  cases  where  great  exactness  is  not  essential  it  is 
possible  to  divide  the  50  c.c.  or  the  100  c.c.  into  two  equal 
parts  by  pouring  into  a  tube  the  exact  counterpart  of  the 
standard  tube  and  matching  the  color.  It  is  even  possible  to 
closely  approximate  the  correct  result  by  the  use  of  a  foot  rule. 
The  standard  is,  we  will  assume,  5  c.c.     The  height  of  liquid  in 


water:  analytical  methods. 


105 


the  tube  to  be  tested,  we  will  call  9  inches.  If  the  height  of 
the  column  left  which  matches  5  c.c.  is  3  inches,  then  the  reading 
was  15  c.c.  of  the  standard. 

The  limit  of  solubility  of  the  mercur-ammonium  iodide  is 
reached  at  25  or  30  c.c.  of  the  standard  in  50  c.c.  The  incipient 
precipitate  not  only  changes  the  color  of  the  solution  but  causes 
a  slight  milkiness  or  turbidity  which  prevents  a  sharp  reading 
of  the  color. 

The  test  is  an  excellent  example  of  quantitive  color  work 
when  carried  out  under  strictly  comparable  conditions. 

It  should  perhaps  be  stated  that  in  both  the  ammonium 
and  nitrite  determinations,  as  also  in  that  of  iron,  dilution  of 
the  sample  in  which  the  color  is  already  developed  does  not 
gi\'e  a  correct  result.  Therefore  dilution  if  necessary  must  be 
made  before  the  reagents  are  added. 

In  order  to  secure  the  most  accurate  results  it  is  impor- 
tant that  the  temperature  of  the  distillates  to  be  nesslerized 
and  of  the  standards  be  the  same,  since  the  warmer  solutions 
give  a  more  intense  color  with  the  Nessler  reagent. 

The  compounds  produced  by  the  action  of  ammonia  on 
mercuric  solutions  are  considered  as  substitutions  of  i  Hg 
for  2H  in  NH4,  and  are  called  mercur-ammoniums.  Tetra- 
mercur-ammonium  iodide  (NHgsI),  the  compound  formed  by 
addition  of  the  Nessler  reagent,  is  a  brown  precipitate,  sol- 
uble in  excess  of  KI  in  the  presence  of  KOH  with  a  brown- 
ish-yellow color  proportional  within  certain  limits  to  the 
amount  of  NH3: 

NH3  +  (2Hgl2  +  2KI  +  3KOH)  =  XHg.I  +  5KI  +  3H2O. 

The  '*  free  ammonia "  in  all  probability  does  not  exist  in 
the  water  in  a  free  state  or  as  the  hydroxide;  it  is  probably 
present  in  the  form  of  carbonate  or  of  chloride.  When  water 
containing  these  or  similar  compounds  of  ammonia  is  boiled, 
they  are  decomposed  and  free  ammonia  passes  off  with  the 


AIR,    WATER,    AND  FOOD. 
lOO 

stean,  and  is  found  in  the  distmate;  hence  the  orig.n  of  the 

"^'"^"  •     .    „   nf   Total    Organic   Nitrogen    by    the 

Determination   of   Total        g  ^^   ^^^ 

TT-  i^ohi    Process. Directions. — Measure    5>j 

Kjeldahl  Process,     u  ,  .    ^  „f  ,=0  c  c.  capacity  and 

water  into  a  round-bottomed  tiask  of  750  cc.      V 


Fio 


.  ,,,_Apparatus  for  DistiU.ng  Ammonia  by  Steam. 


WATER.   ANALYTICAL   METHODS.  I07 

gauze  under  the  hood  and  boil  cautiously  until  the  water  is 
all  driven  off.  Place  a  small  funnel  iU:  the  neck  of  the  flask 
to  prevent  the  escape  of  acid  fumes,  and  continue  the  heating 
for  at  least  half  an  hour  after  the  sulphuric  acid  beco.r.es 
white.  Meanwhile  rinse  out  the  distilling  apparatus  (see 
Fig.  10),  and  free  it  from  ammonia  as  usual.  Then,  after  the 
acid  in  the  digestion-tiask  has  cooled,  rinse  down  the  neck 
of  the  f^ask  with  loo  c.c.  of  ammonia-free  water  and  attach 
the  flask  to  the  distillation  apparatus.  Add  lOO  c.c.  of 
potassium  hydroxide  solution  through  the  separatory  funnel 
and  distil  off  the  ammonia  by  steam,  receiving  the  distillate 
in  a  250-c.c.  graduated  flask.  Conduct  the  distillation  rather 
slowly  until  the  first  50  c.c.  have  distilled  ov^r;  then  distil 
more  rapidly  until  about  175  c.c.  have  been  collected.  Make 
the  volume  of  the  distillate  up  to  250  c.c.  with,  ammonia-free 
water,  mix  it  thoroughly  and  take  50  c.c.  for  nesslerization. 

Notes. — The  principles  involved  in  the  method  consist  in 
the  oxidation  of  the  carbon  and  hydrogen  of  the  organic  mat- 
ter by  boiling  sulphuric  acid,  the  nitrogen  being  converted 
into  ammonia  and  held  by.  the  acid  as  ammonium  sulphate. 
The  ammonia  is  then  liberated  and  distilled  off  from  an  alka- 
line solution.  The  use  of  mercury  and  of  potassium  per- 
manganate to  assist  in  the  oxidation  has  been  found  to  be 
unnecessary,  as  the  organic  matter  in  natural  waters  is  much 
more  easily  oxidized  than  in  other  substances, — flour,  for  in- 
stance. The  presence  of  nitrates  and  nitrites  in  waters  has 
not  been  found  to  interfere  with  the  accurate  determination 
of  the  organic  nitrogen.  The  error  which  has  been  found  by 
Kjeldahl  and  Warrington  to  be  caused  by  the  presence  of 
nitrates  seems  to  disappear  when  the  organic  material  is 
diluted  to  the  considerable  extent  that  exists  in  natural 
waters.     The  hisfh  chlorine  found  in  some  well-waters  does 


Io8  AIR,    WATER,    AND    FOOD. 

not  interfere  with  the  method  to  any  extent,  but  this  deter- 
mination does  not  possess  much  vakie  in  this  class  of  waters, 
which  are  low  in  organic  nitrogen. 

In  carrying  out  the  digestion  with  sulphuric  acid,  the 
greatest  care  must  be  taken  to  prevent  access  of  ammonia  or 
dust  from  any  source.  The  acid  solutions  will  absorb  am- 
monia from  the  air  or  from  the  dust  of  the  laboratory  if  they 
are  allowed  to  remain  uncovered  for  any  length  of  time. 
This  source  of  error  may  in  some  instances  be  sufficiently 
large  to  render  a  determination  valueless,  even  in  a  room 
which  is  to  all  appearances  free  from  ammonia-fumes. 
Hence  the  operation  should,  if  possible,  be  carried  to  com- 
pletion within  twenty-four  hours,  and  for  every  set  of  deter- 
minations a  blank  analysis  should  be  made  with  ammonia- 
free  water  in  order  to  make  a  correction  for  the  ammonia  in 
the  reagents,  and  for  that  accidentally  introduced  during  the 
process. 

As  the  result  of  many  hundred  comparative  determina- 
tions of  thp  organic  nitrogen  and  of  the  albuminoid  ammo- 
nia in  natural  waters  which  take  their  origin  in  the  glacial 
drift,  it  has  been  found  that  the  nitro^^en  given  by  the  albu- 
minoid-ammonia process  as  directed  in  the  previous  pages 
is  about  one-half  of  the  total  organic  nitrogen  as  given  by  the 
Kjeldahl  process;  in  the  case  of  sewages  and  polluted  waters 
it  is  very  variable  owing  to  their  irregular  composition. 

Determination  of  Nitrogen  in  the  Form  of  Nitrites. 
— Directions. — When  the  determination  of  the  free  and 
albuminoid  ammonia  is  w^ell  under  way,  the  estimation  of 
nitrogen  in  the  next  stage  of  decay,  that  of  nitrites,  should 
be  begun.  If  the  water  is  colorless,  measure  out  the  required 
amount,  usually  lOO  c.c,  into  a  loo-c.c.  tube.  If  the  water 
possesses  color  which  cannot  be  removed  by  simple  filtra- 
tion, it  should  be  decolorized  as  follows:    Thoroughly  rinse 


water:  analytical   methods.  109 

with  the  water  a  250-c.c.  glass-stoppered  bottle;  pour  into 
it  about  200  ex.  of  the  sample,  add  about  3  c.c.  of  the  milk 
of  alumina  and  shake  the  bottle  vigorously.  Let  the  bottle 
stand  for  ten  or  fifteen  minutes  and  filter  through  a  small 
plaited  filter  which  has  been  thoroughly  washed  with  water 
free  from  nitrites.  From  this  filtrate  take  10  c.c.  for  nitrates 
(see  p.  no).  To  100  c.c.  of  the  filtered  sample  or  of  the  origi- 
nally colorless  water  add  10  c.c.  of  sulphanilic  acid  in  acetic 
acid  and  10  c.c.  of  naphthylamine  acetate. 

After  standing  5  to  10  minutes,  not  longer,  compare  with 
the  standards  made  with  the  nitrite  solution  or,  better,  with 
2x4  inch  pieces  of  Milton  Bradley's  standard  papers*  the  VR, 
violet-red  tint  2  which  is  an  exact  match  for  the  color  given 
by  5  c.c.  or  VR,  tint  i,  which  matches  10  c.c.  of  the  stand- 
ard nitrite  solution  in  a  loo-c.c.  Nessler  tube  with  a  depth 
of  5  inches  to  the  graduation.  If  100  c.c.  of  the  sample  is  used 
this  measures  the  nitrites  in  parts  per  million.  Good  waters, 
show  considerably  less  than  .005,  suspicious  waters  between 
.005  and  .010,  bad  waters  may  show  from  .000  to  .300  or  even 
more.  The  same  use  of  the  foot  rule  and  aliquot  part  may 
be  made  as  above  in  the  ammonia  determination. 

One  cubic  centimeter  of  the  standard  nitrite  solution  contains 
0.000000 1  gram  N  as  nitrite.  The  determination  must  be 
completed  within  half  an  hour,  since  the  air  of  a  room  in  which 
gas  is  burned  contains  nitrites. |  ,  , 

Notes. — If  the  color  obtained  is  more  than  that  given  by 
20  c.c.  of  the  standard  solution,  as  it  may  be  in  the  case  of 
water  from  bad  wells  and  sewage  effluents,  the  water  should 
be  diluted  with  nitrite-free  water,  10  c.c.  or  even  i  c.c.  being 
made  up  to  100  c.c.  before  adding  the  reagents,  since  colors 

*  Mulliken's   "Identification  of  Pure  Organic  Compounds,"  Sheet  A,  Color 
Standard. 

t  Defren:    Tech.  Quart.,  g  {1896),  238;    Axson:    loc.  cit.,  12  {1899),  219. 


no  AIR,   WATER,    AND    FOOD. 

above  20  c.c.  are  too  deep  for  accurate  comparison.  In  many 
cases,  however,  it  may  be  more  convenient  and  sufficiently 
accurate,  where  the  colors  are  not  very  much  greater  than 
20  ex.,  to  read  the  color  in  an  aliquot  part,  as  described  in 
the  determination  of  ammonia  on  page  104. 

The  reactions  which  take  place  consist  first  in  the  diazotiz- 
ing  of  the  sulphanilic  acid  by  the  nitrite  present  in  acid  solu- 
tion, forming  diazobenzenesulphonic  anhydride.  This  reac.s 
with  the  naphtylamine  hydrochlorate,  forming  azo-«-amido- 
naphtylic  parabenzol-sulphonic  acid,  which  gives  the  pink 
color  to  the  solution,  the  amount  formed  depending  upon 
the  amount  of  nitrite  present. 

N  ■  N         H 

I  I  I 

c  c       c 

/\  /\/  \ 

H— C         C— H         H— C         C         C— H 

II  I  I  II  I 

H— C         C— H         H— C         C         C— H 

\//  \  /\  // 

c  c       c 

I  I      I 

SO,H  NH,      H 

Determination  of  Nitrogen  in  the  Form  of  Nitrates.* 

— Directions. — Nitrogen  in  the  fourth  stage,  that  of  nitrates, 
is  next  determined.  In  the  case  of  groxmd-waters,  or  sewage 
effluents,  measure  2  c.c.  from  the  bottle  with  a  capillary  pipette, 
into  a  three-inch  porcelain  evaporating-dish;  for  surface- 
waters,  always  low  in  nitrates,  take  10  c.c.  from  the  portion 
already  decolorized  in  the  determination  of  the  nitrites.  Place 
the  dishes  on  the  top  of  the  water-bath  and  let  their  contents 
evaporate  gently  until  one  or  two  drops  are  left;  then  set  them 
away  in  a  place  free  from  dust,  that  the  remainder  may  evapo- 
rate spontaneously.  Do  not  let  them  go  quite  to  dryness  on 
the  bath. 


♦Sprengel:    Pogg.   Ann.,    121,    188.     Grandval  and   Lajoux:     Compt.  rend., 
loi,  62.     Gill:  /.  Am.  Chem.  Soc,  16  {1894),  122. 


water:    analytical  methods.  hi 

When  the  water  is  entirely  evaporated,  drop  six  drops  of 
phenol-disulphonic  acid  directly  upon  the  dry  residue  and 
rub  it  around  with  a  glass  rod  to  insure  complete  contact  of 
the  acid  and  the  residue  in  the  dish.  Dilute  the  acid  with 
7  ex.  of  distilled  water  and  add  3  c.c.  of  ammonium  hydrate 
(i:i)  or  if  only  one  laboratory  is  available  KOH  (1:3)  since 
no  ammonium  hydrate  solutions  should  be  allowed  in  a  distilling 
laboratory. 

To  prepare  the  standards  to  be  matched  in  the  small  porce- 
lain dishes,  measure  out  the  varying  amounts  of  the  standard 
nitrate  solution,  for  instance  0.5,  i.o  c.c.  to  8  c.c,  add  enough 
water  to  make  the  volume  10  c.c.  and  two  or  three  drops  of  the 
alkaline  hydrate. 

For  very  low  or  very  high  colors  the  matching  is  most 
satisfactorily  done  in  50-c.c.  Nessler  tubes,  diluting  to  50  c.c. 
or  reading  an  aliquot  portion.  For  matching  the  lowest  colors, 
which  in  this  case  is  safely  done,  5  or  6  inch  high  tubes  cut 
from  broken   Nessler   tubes   are   very  satisfactory. 

To  prepare  standards  in  Nessler  tubes.  A  portion  of  water 
is  made  alkaline,  and  the  standard  is  run  in  little  by  little  until 
it  matches  the  lowest  color.  Then  more  is  added  until  the  next 
color  is  matched,  and  so  on  to  the  highest  color. 

Notes. — It  will  be  found  that  if  10  c.c.  of  a  colored  water 
be  evaporated  directly,  the  color  obtained  with  the  reagents 
will  be  much  deeper  as  well  as  browner  than  that  given  by 
the  standards;  hence  the  necessity  for  first  decolorizing. 

Chlorides  interfere  with  the  accuracy  of  the  method,  but 
not  to  any  extent  when  chlorine  is  present  in  less  than  20  parts 
per  miUion.  If  the  amount  of  chlorine  be  more  than  this,  the 
evaporation  should  be  made  in  vacuo  over  sulphuric  acid. 
Nitrites  do  not  interfere  with  the  test. 

The  reaction  is  generally  considered  to  consist  in  the 
formation  of  picric  acid.  While  this  is  not  quantitatively 
true,  it  offers  the  best  explanation  of  the  changes  that  occur. 


112  AIR,  WATER,    ANID    FOOD. 

Trinitrophenol  (picric  acid)  is  formed  by  the  action  of  the 
nitrates  in  the  cold,  dry  residue  upon  the  phenol-disulphonic 
acid  with  which  it  is  moistened: 

OH  OH 

I  I 

c  c 

/  \  /  ^ 

H— C         C— SO3H  NO— C         C— NO, 

II  I  +3HN03=  !1  I  +2H,S0, 

H— C         C— H  H— C         C— H 

\  //  \  //  +Hfi 

C  C 

I  I 

SO3H  NO, 

Phenol-disulphonic  acid.  Picric  acid. 

The  addition  of  an  excess  of  caustic  alkali  converts  the 
picric  acid  to  the  alkali  picrate,  which  imparts  an  intense  yel- 
low color  to  the  liquid.  The  best  color  is  obtained  by  the 
use  of  ammonia. 

Large  quantities  of  nitrates  in  colorless  water  may  be  de- 
termined by  reduction  to  ammonia  by  sodium  amalgam,  or 
by  any  reaction  which  yields  nitrogen,  this  being  measured  as  gas. 

Determination  of  the  Carbonaceous  Matter  or  "  Oxy- 
gen Consumed." 

KiibcFs  Hot  Acid  Method, 

Reagents. — Ammonium  oxalate  0.888  gram  in  one  liter 
distilled  water.  One  c.c.  is  equivalent  to  o.oooi  gram  of 
oxygen.  Potassium  permanganate  0.4  gram  in  one  liter  dis- 
tilled water,  standardize  against  the  ammonium  oxalate  solution 
and  make  the  necessary  correction.  If  exact,  i  c.c.  is  equivalent 
to  0.0001  gram  available  oxygen. 

Directions. — Measure  100  c.c.  of  the  water  into  a  250-c.c. 
flat-bottomed  flask,  add  10  c.c.  of  sulphuric  acid  (1:3)  and 
about  10  c.c.  of  the  potassium  permanganate.  Place  the  flask 
on  wire  gauze  and  heat  it  quickly  to  boiling.  Boil  the  solution 
for  exactly  two  minutes;  remove  it  from  the  flame;  let  it  cool 
one  minute,  and  add  10  c.c.  of  the  ammonium  oxalate.     Titrate 


water:  analytical  method.  115 

with  the  permanganate  to  a  faint  permanent  pink  color.  Each  c.c. 
of  the  exact  permanganate  used  in  excess  of  the  oxalate  solution 
used  represents  o.oooi  gram  of  oxygen  consummed  by  the  sample. 

Notes. — For  highly  colored  surface-waters  25  c.c.  are 
taken  and  diluted  to  100  c.c.  with  water  free  from  organic 
matter;   for  sewages  10  c.c.  are  diluted  in  the  same  way. 

The  oxygen  given  up  by  the  permanganate  combines 
with  the  carbon  of  the  organic  matter  and  perhaps  to  a  cer- 
tain extent  with  the  hydrogen,  but  not  with  the  nitrogen. 
The  amount  of  oxygen  consumed  bears  some  relation,  there- 
fore, to  the  amount  of  organic  carbon  present  in  the  water,, 
but  this  relation  certainly  cannot  be  taken  as  a  definite  one 
in  every  case,  the  results  varying  even  with  the  time  of 
boiling.  The  method  has  its  greatest  value  when  it  is 
used  to  compare  waters  of  the  same  general  character  and 
having  the  same  origin;  for  example,  in  making  periodical 
tests  of  the  purity  of  the  effluent  from  a  filter.  Furthermore, 
in  order  that  the  results  shall  have  this  comparative  value, 
it  is  absolutely  necessary  that  the  process  shall  always  be 
carried  out  in  exactly  the  same  way,  even  to  the  minutest 
detail  of  quantity,  time,  and  temperature. 

In  some  cases  it  may  be  found  advantageous  to  heat  the 
solution  upon  the  water-bath  for  half  an  hour  instead  of  boil- 
ing it  for  five  minutes.  The  results,  however,  will  not  be 
exactly  comparable  with  those  obtained  by  boiling. 

Different  kinds  of  organic  matter  behave  differently  with 
various  oxidizing  agents,  so  that  a  comparison  of  the  results 
obtained  with  different  oxidizing  agents  may  t1-^ow  light 
upon  the  character  of  the  ors^anic  matter,  as  wel^  as  i^s 
amount.*  In  waters  from  the  watersheds  of  f^a^^tet-n  Nor'h 
America  the  color  and  the  oxveen  consumed  have  a  certain, 
though  somewhat  varying,  relation. 

Determination  of  Chlorine. — The  chlorine  is  deter- 
mined  in   natural   waters   by   the   method   in   general   use; 

*  Woodman:  /.  Am.  Chem.  Soc,  20  {rSgS),  497. 


114  AIR,    WATER,    AND    FOOD. 

namely,  titration  with  a  solution  of  silver  nitrate,  using"  potas- 
sium chromate  as  an  indicator.  Since  the  exact  change  of 
color  which  constitutes  the  end-point  will  vary  with  the 
sensitiveness  of  the  eyes  of  different  observers  to  red,  each 
person  should  standardize  the  silver  nitrate  solution  for  him- 
self. To  do  this,  measure  into  a  six-inch  porcelain  dish  25 
c.c.  of  distilled  water;  add  5  c.c.  of  sodium  chloride  solution 
(i  c.c.  —  0.001  gram  CI)  from  the  burette  and  three  drops  of 
potassium  chromate  solution.  Titrate  with  the  silver  nitrate 
solution  until  the  yellow  color  of  the  liquid  assumes  the  faint- 
est tinge  of  reddish  brown. 

Directions. — Waters  which  are  high  in  chlorine,  i.e.,  which 
contain  20  or  more  parts  per  million,  are  titrated  directly, 
using  25  c.c.  either  with  or  without  the  addition  of  5  c.c.  of 
the  salt  solution.  Waters  which  are  low  in  chlorine  are  con- 
centrated before  titration,  250  c.c.  being  evaporated  to  25  c.c. 
on  the  water-bath.  Brown  surface-waters  should  be  decol- 
orized as  follows:  Pour  into  a  750-c.c.  flat-bottomed  flask 
about  500  c.c.  of  the  water.  Add  3  c.c.  of  the  milk  of 
alumina;  shake  and  heat  the  water  quickly  to  boiling  on  an 
iron  plate.  When  the  liquid  comes  to  a  full  boil,  at  once 
remove  the  flask  from  the  plate  to  avoid  loss  by  evaporation. 
Place  it  in  an  inclined  position  to  allow  the  alumina  to  settle. 
Decant  of¥  250  c.c.  of  the  colorless  water  into  a  six-inch  dish 
for  concentration  to  25  c.c,  using  a  flask  calibrated  for  both 
the  hot  and  the  cold  solution.  Before  making  the  titration, 
rub  down  the  sides  of  the  dish  above  the  liquid  with  a  small 
quantity  of  distilled  water  free  from  chlorine,  using  a  clean 
feather.  Rinsing  alone  will  not  always  dissolve  the  chlo- 
rides which  adhere  to  the  sides  of  the  dish. 

Notes. — For  titration  by  this  method  the  solution  must 
be  as  nearly  neutral  as  possible  If  the  water  is  alkaline  to 
.any  extent,  it  should  be  neutralized  with  dilute  sulphuric  acid, 


WATER:    ANALYTICAL    METHODS.  II5 

using  phenolphthalein  as  an  indicator.  The  solution  will 
then  contain  alkali  only  as  bicarbonate,  which  does  not 
interfere  with  the  titration.  Acid  water  must  be  made  neu- 
tral by  the  addition  of  sodium  carbonate. 

It  is  important  that  the  process  be  carried  out  essentially 
as  described,  since  it  has  been  found  that  the  results  vary 
wath  the  volume  of  solution  in  which  the  titration  is  made, 
the  amount  of  chromate  used,  and  the  amount  of  precipitated 
silver  chloride  present.*  A  correction  for  volume  can  be 
made  by  means  of  the  formula  given  by  Hazen. 

E.  G.  Smith  t  recommends  titration  in  a  volume  of 
100  C.C.,  making  a  correction  of  .1  c.c.  more  or  less  as  found 
for  the  error  due  to  dilution  of  the  reagents. 

Color  is  removed  by  agitation  with  milk  of  alumina  as 
before  described. 

Determination  of  the  Residue  on  Evaporation  and 
the  Loss  on  Ignition. — Directions. — Ignite  and  weigh  a 
platinum  dish.  Measure  into  it  loo  c.c.  of  the  water  (200 
'C.c.  in  the  case  of  surface-waters),  and  evaporate  to  dryness 
on  the  water-bath.  When  the  water  is  all  evaporated  heat 
the  dish  in  the  oven  at  the  temperature  of  boiling  water  for 
two  hours,  then  let  it  remain  in  a  desiccator  over  sulphuric 
acid  for  several  hours  and  weigh4  The  increase  in  weight 
gives  the  '*  total  soHds  "  or  "  residue  on  evaporation."  If 
from  a  ground-water,  save  the  residue  for  the  determination 
of  the  iron. 

In  the  case  of  surface-waters  the  residue  should  be  ignited 
and  the  loss  on  ignition  noted.  Heat  the  dish  in  a  "  radia- 
tor," which  consists  of  another  platinum  dish  enough  larger 
to  allow  an  air-space  of  about  half  an  inch  between  the  two 
dishes,  the  inner  dish  being  supported  by  a  triangle  of  plati- 
num  wire.      Over  the  inner  dish   is   suspended   a   disk   of 

*  Hazen:  Am.  Chem.  Jour.,  ii  {i88g),  409. 

•j-  Trans.   Wis.  Acad.  Sciences,  Arts,  and  Letters,  VoL  XIII,  359. 

Jin  some  laboratories  it  is  the  practice  to  dry  at  110°  or  130°  C. 


Il6  AIR,    WATER,    AND    FOOD. 

platinum-foil  to  radiate  back  the  lieat  into  the  dish.  The 
larger  platinum  dish  is  heated  to  1)ri2^ht  redness  by  a  triple 
gas-burner.  Heat  the  dish  in  the  radiator  until  the  residue  is 
white  or  nearly  so.  Note  any  blackening  or  charring  of  the 
residue  and  any  peculiar  "  burnt  odor  "  which  may  be  given 
off.  After  the  dish  has  cooled,  slightly  moisten  the  residue 
with  a  few  drops  of  distilled  water  to  secure  weighing  under 
the  same  conditions.  Heat  the  residue  in  the  oven  for  half  an 
hour;  cool  in  a  desiccator  and  weigh.  This  gives  the  weight 
of  '*  fixed  solids,"  the  difference  being  the  ''  loss  on  ignition.'* 

Notes. — Before  the  introduction  of  modern  methods  of 
water-analysis  the  determination  of  ''  loss  on  ignition  "  was 
the  only  method  for  the  estimation  of  organic  matter  in 
water.  In  order,  however,  that  the  determination  shall  pos- 
sess any  real  value,  it  is  necessary  to  regulate  carefully  the  heat 
during  the  ignition,  so  as  to  destroy  the  organic  matter  with- 
out decomposing  calcium  carbonate  or  volatilizing  the  alkali 
chlorides. 

This  is  what  the  use  of  the  radiator  is  intended  to  accom- 
plish, and  in  the  case  of  surface-waters,  with  low  mineral  con- 
tent and  considerable  organic  matter,  the  method  gives  gen- 
erally satisfactory  results.  But  in  the  case  of  ground-waters 
having  little  or  no  organic  matter  and  high  mineral  content 
the  loss  is  often  very  great  on  account  of  the  decomposition 
of  nitrates  and  chlorides  of  the  alkaline  earths  and  the  loss  of 
water  of  crystallization.  In  waters  of  this  class  the  determi- 
nation of  "  loss  on  ignition  "  is,  therefore,  generally  meaning- 
less, although  an  approximation  to  the  amount  of  organic 
matter  can  be  obtained  by  the  addition  of  sodium  carbonate  to 
the  water  before  evaporating  to  dryness.  By  this  means  the 
alkaline  earths  are  precipitated  as  carbonates,  the  chlorine 
and  nitric  acid  are  held  by  an  alkaline  base,  and  there  is  no 
water  of  crystallization  in  the  residue.  Even  with  this  modi- 
fication the  loss  is  considerable  when  magnesium  salts  are 
present,  owing  to  the  loss  of  carbonic  acid. 


WATKR:    ANALYTICAL    METHODS. 


117 


The  behavior  on  ignition  is  oftentimes  significant. 
Swampy  or  peaty  waters  give  a  brownish  residue  on  evapora- 
tion to  dryness,  which  blackens  or  chars,  and  this  black  sub- 
stance burns  off  quite  slowly.  The  odor  of  the  charring  is 
like  that  of  charring  wood  or  grain;  sometimes  sweetish,  but 
not  at  all  offensive.  Waters  much  polluted  by  sewage  blacken 
slightly;  the  black  particles  burn  off  quickly  and  the  odor  is 
disagreeable.  Any  observations  on  this  point  should  be  re- 
corded in  the  report  (p.  141 )  under  the  heading  "  Change  on 
Ignition." 

Determination  of  the  Hardness. 

I.  By  Soap. — Clark's  Method. 

Directions. — Measure  50  c.c.  of  water  into  a  200-c.c.  clear 
glass-stoppered  bottle  and  add  the  soap  solution  from  the 
burette,  two  or  three  tenths  of  a  cubic  centimeter  at  a  time, 
-shaking  well  after  each  addition,  until  a  lather  is  obtained 
which  covers  the  entire  surface  of  the  liquid  with  the  bottle 
lying  on  its  side,  and  is  permanent  for  five  minutes.  The 
number  of  parts  of  calcium  carbonate  corresponding  to  the 
volume  of  soap  solution  used  is  found  in  the  table  in  Appen- 
dix A. 

This  will  give  the  total  hardness.  If  it  is  desired  to  find 
the  permanent  hardness  also,  dilute  50  c.c.  of  the  water  to 
about  200  c.c.  and  boil  down  to  50  c.c.  in  a  beaker,  cool  and 
determine  the  hardness  as  before.  This  will  give  the  per- 
manent hardness,  and  the  difference  will  be  the  temporary 
hardness. 

Notes. — When  potassium  or  sodium  soap  is  added  to 
water  containing  calcium  and  magnesium  salts,  the  soap  is 
decomposed,  and  insoluble  compounds  with  the  fatty  acids 
are  formed.  The  importance  of  adding  the  soap  in  small  quan- 
tities cannot  be  too  strongly  emphasized,  especially  in  the 
presence  of  magnesium  compounds.     The  presence  of  mag- 


Il8  AIR,    WATER,    AND   FOOD. 

nesium  salts  will  be  recognized  by  the  peculiar  curdy  appear- 
ance of  the  precipitate  formed  and  by  the  occurrence  of  a 
false  end-point,  the  lather  lasting  about  three  minutes  when 
the  titration  is  about  half  done.  If  much  carbonic  acid  be 
liberated,  it  is  better  to  follow  Dr.  Clark's  original  directions 
and  remove  it  by  suction. 

By  reference  to  the  table  it  will  be  observed  that  values 
are  not  given  fcr  more  than  i6  c.c.  of  the  soap  solution.  If 
in  any  case  the  water  under  examination  requires  more  than 
10  c.c.  of  the  standard  soap  solution,  a  smaller  portion  of 
25  c.c,  10  c.c.  or  even  2  c.c,  as  the  case  may  require,  is  meas- 
ured out  and  made  up  to  a  volume  of  50  c.c  with  recently 
distilled  water.  If  the  volume  of  soap  used  is  always  about 
7  c.c,  this  will  keep  the  results  comparable  with  each  other, 
although  the  element  of  dilution  introduces  an  error.  Potable 
w^aters,  in  the  eastern  United  States,  at  least,  are  rarely  so 
high  in  mineral  matter  as  to  require  excessive  dilution.  In 
the  case  of  extremely  hard  waters,  however,  the  acid 
method  is  to  be  preferred.  Distilled  water  itself,  containing 
no  calcium  salt  whatever,  requires  the  use  of  a  considerable 
quantity  of  soap  to  produce  a  permanent  lather.  The  cause 
for  this  seems  to  exist  in  the  dissociation  of  the  greater  part 
of  the  soap  at  the  extreme  dilution  to  which  it  is  subjected,, 
and  the  slow  accumulation  of  a  sufficient  quantity  of  undis- 
sociated  soap  to  allow  of  the  increase  of  surface  tension  to  a 
point  at  which  soap-bubbles  will  persist. 

By  the  temporary  hardness  of  water  is  meant  the  hardness 
which  is  removed  by  boiling.  It  is  due  to  the  carbonates  of 
calcium  and  magnesium  held  in  solution  by  the  carbonic  acid 
in  the  water,  probably  in  the  form  of  bicarbonates.  Perma- 
nent hardness  is  that  which  is  not  removed  by  boiling.  It  is. 
caused  by  the  presence  of  soluble  salts  of  calcium  and  mag- 
nesium, not  carbonates,  but  chlorides  and  sulphates  princi- 
pally, held  in  solution  by  the  solvent  power  of  the  water  itself.. 


WATER:  ANALYTICAL  METHOD.  1 1 9* 

2.  By  Acid. — Hehner's  Method* 

ALKALINITY. 

Directions. — For  the  determination  of  the  "  alkalinity," 
measure  loo  ex.  of  the  water  into  a  clear  bottle  such,  as  is  used 
for  the  soap  test,  and  add  2.5  c.c.  of  the  erythrosine  indicator, 
0,1  gram  of  the  sodium  salt  in  i  liter  of  distilled  water,  and 
5  c.c.  of  chloroform  neutral  to  erythrosine.     Mix  well  by  shaking 

N 

and  add  —  sulphuric  acid  from  the  burette  in  small  quantities, 

shaking  thoroughly  after  each  addition.  The  pink  color  grad- 
ually grows  lighter  until  the  addition  of  a  drop  or  two  of  the 
acid  causes  it  to  disappear  entirely.  Each  tenth  of  a  cubic 
centimeter  of  acid  used  represents  one  part  of  CaCOs  in  1,000,000.. 
Make  a  correction  for  the  indicator  by  carrying  out  a  blank 
determination  with  distilled  water. 

The  alkalinity  may  be  determined  more  quickly  as  follows. 
Measure  100  c.c.  of  the  water  to  be  tested  into  a  No.  6  evapo- 
rating dish,  add  two  drops  of  sensitive  methyl  orange  and  titrate 

N  .  . 

with  the  —  sulphuric  acid.     Lacmoid  and  phenacetolin  can 

also  be  used  in  the  determination  of  the  alkalinity,  but  they 
necessitate  titration  in  a  hot  solution  on  account  of  their  sus- 
ceptibility to  carbonic  acid. 

Notes. — This  method  is  especially  useful  for  waters  which 
require  clarification  by  alumina  and  subsequent  filtration. 

The  use  of  chloroform  is  essential  to  secure  a  sharp  end- 
point.  The  non-ionized  erythrosine  formed  by  the  addition 
of   the  acid  to    its   alkali  salt    is   soluble  in  the  aqueous  solu- 


*  Hehner:    Analyst,  i88^,  8,  77;    Draper,  Chem.  News,  188^,  51,  206:    EUms: 
Jour.  Am.  Chem.  Soc,  i8gg,  21,  239. 


I20  AIR,    WATER,   AND    FOOD. 

tion  with  a  slight  rose  color.  It  is,  however,  more  soluble 
in  the  chloroform,  and  when  it  is  thus  removed  as  fast  as 
formed  the  neutraHzation  of  the  alkali  becomes  at  once 
apparent.* 

If  a  water  contains  sodium  or  potassium  carbonate, 
there  will  not  be  any  permanent  hardness,  and  hence  more 
acid  will  be  required  for  the  filtrate  than  corresponds  to  the 
amount  of  sodium  carbonate  added.  From  the  excess 
the  amount  of  sodium  carbonate  in  the  water  may  be 
determined.  Any  alkali  carbonate  present  would  be 
calculated  as  temporary  hardness  by  the  direct  titration; 
hence  it  should  be  calculated  to  calcium  carbonate  and 
subtracted  from  the  results  found  by  the  direct  titra- 
tion. 

Determination  of  Phosphsites. -f^Directtons. — Evapo- 
rate 50  c.c.  of  the  water  and  3  c.c.  of  nitric  acid  (sp.  gr.  1.07) 
to  drvness  in  a  3 -inch  porcelain  dish  on  the  water-bath. 
Heat  the  residue  in  an  oven  for  two  hours  at  the  tempera- 
ture of  boiling  water.  Treat  the  dry  residue  with  50  c.c. 
of  cold  distilled  water,  added  in  several  portions  and  poured 
into  the  comparison-tube.  It  is  not  necessary  to  filter  the 
solution.  Add  4  c.c.  of  ammonium  molybdate  (50  grams 
per  Hter)  and  2  c.c.  of  nitric  acid,  mix  the  contents  of  the 
tube  and  compare  the  color,  after  three  minutes,  with  stand- 
ards made  by  diluting  varying  quantities  of  the  standard 
phosphate  solution  (i  c.c,  =0.0001  gram  Pfi^)  to  50  c.c.  with 
distilled  water  and  adding  the  reagents  as  above.  Carry 
out  a  blank  determination  on  the  distilled  water  used  for 
dilution,  especially  if  it  has  stood  for  any  length  of  time  in 
glass  vessels. 


*  Ellms:    J.  Ant.  Chem    Soc,  21   (iSqq),  359. 

tLepierre-     Bull.    Soc.    Chtm.,    15    {i8q6),    1213       Woodman    and    Cayvan: 
J.  Am.  Chem.  Soc.  23  (iQOl),  96.     Woodman-  ibid.  (IQ02),  735. 


WATER:    ANALYTICAL    METHODS.  121 

Notes. — The  method  as  described  will  be  sufficient  for 
ordinary  work.  If  a  more  exact  determination  of  the  phos- 
phate is  required,  a  slight  correction  should  be  made  in  each 
case.  For  a  table  showing  these  corrections  reference  may- 
be made  to  the  paper  by  Woodman  and  Cay  van  previously 
cited. 

The  evaporation  and  heating  with  nitric  acid  is  for  the 
purpose  of  removing  silica,  which  gives  with  ammonium 
molybdates  a  yellow  color  similar  to  that  given  by  phos- 
phates. 

The  determination  of  phosphates  in  a  drinking-water  is 
a  matter  which  has  not  received  the  attention  from  water 
analysts  that  has  been  given  to  the  estimation  of  various 
other  constituents.  Any  one  who  looks  through  the  litera- 
ture cannot  help  noticing  how  few^  are  the  published 
results  of  quantitative  estimations  of  the  phosphate  con- 
tent of  natural  waters,  apart  from  mineral  waters.  Yet 
this  determination,  by  reason  of  the  conversion  of 
organic  phosphorus  compounds  into  phosphates  through 
the  processes  of  decay,  is  one  which  might  reasonably 
be  expected  to  throw  considerable  light  on  the  question 
of  the  pollution  of  natural  waters  by  objectionable  ma- 
terial. 

The  reasons  for  this  dearth  of  published  data  are  not 
far  to  seek.  To  be  of  value  the  amount  of  phosphate  must 
be  known  within  rather  narrow  limits.  Qualitative  tests 
are  not  sufficient.  The  mere  presence  of  phosphates  is  by 
no  means  definite  or  even  confirmatory  evidence  of  organic 
pollution.  Rocks  and  minerals  containing  phosphates  are 
found  nearly  everywhere,  and  traces,  at  times  even  con- 
siderable quantities,  may  be  dissolved,  especially  by  waters 
rich  in    carbonic    acid.      This,  however,  does    not    constitute 


122  AIR,    WATER,    AND    FOOD. 

a  serious  objection  to  the  utility  of  the  determination.  The 
same  is  true  of  many  if  not  most  of  the  constituents  upon 
which  reHance  is  plac-ed  in  judging  of  the  quaUty  of  a  water. 
Unpolluted  w^aters  often  contain  notable  amounts  of  nitrates 
and  chlorides,  and  a  true  judgment  can  be  rendered  only 
after  comparison  with  samples  from  adjacent  but  unpol- 
luted sources. 

The  chief  reason,  however,  has  been  the  lack  of  an  accu- 
rate and  simple  method,  sufficiently  delicate,  and  of  enough 
data  to  work  out  a  standard  for  comparison. 

This  reason  can  hardly  hold  true  now^  for  enough  w^ork 
has  been  done  on  the  colorimetric  method  to  indicate  its 
value  as  another  link  (of  which  w^e  have  none  too  many,  any- 
way) in  the  chain  of  circumistantial  evidence  by  which  we 
are  often  compelled  to  judge  the  purity  of  a  water. 

The  amount  of  phosphate  and  its  variation  seem  to  fol- 
low the  same  general  line  as  the  other  mineral  constitu- 
ents which  either  accompany  the  polluting  material  or  are 
produced  by  its  decay,  especially  the  nitrates  and  chlorides. 
It  is  not,  however,  so  delicate  an  indicator  as  these.  In 
general  it  may  be  said  that  the  amount  (expressed  as  P2O5) 
in  an  unpolluted  w^ater  will  seldom  be  over  i.o  part  per 
million. 

Determination  of  Iron.* — Directions. — Evaporate  100  or 
200  c.c.  of  the  water  to  dryness  in  a  platinum  dish.  (The 
weighed  residue  from  the  determination  of  total  solids  may 
be  used  if  desired.)  Treat  the  residue  with  5  c.c.  of  hydro- 
chloric acid  (i :  i),  being  careful  to  carry  the  acid  to  the  edge 
of  the  dish.  In  some  cases  it  may  be  necessary  to  heat  the 
dish  gently  on  the  water-bath  in  order  to  bring  all  the  iron 

*  Thomson:    J.  Chem.  Soc,  67  (iSSj),  493. 


WATER:    ANALYTICAL    METHODS. 


123 


into  solution.  VV'hen  all  is  dissolved  with  the  exception  of 
silica,  rinse  the  solution  into  a  loo-c.c.  tube  and  make  it  up 
to  c.bout  50  c.c.  with  distilled  water.  Add  a  solution  of  po- 
tassium permanganate  drop  by  drop  until  the' solution  re- 
mains pink  for  10  minutes. 

^leanwhile  prepare  a  blank  standard  with  50  c.c.  of  dis- 
tilled water  and  about  a  cubic  centimeter  of '  hydrochloric 
acid.  Add  15  c.c.  of  potassium  sulphocyanide  solution  'to 
the  waters  and  to  the  blank  standard.  Add  the  standard 
iron  solution,  in  small  quantities,  .02  c.c.  if  necessary,  from 
a  capillary  pipette,  mixing  thoroughly  by  pouring  the  solu- 
tion back  and  forth  from  one  tube  to  another  ■  after  each 
addition,  until  the  color  of  the  standard  matches  that  of 
the  water.  One  cubic  centimeter  of  the  standard  iron  solu- 
tion is  equal  to  0.000 1  gram  of  Fe.  '  ' 

Notes. — In  the  case  of  some  river- waters  it  Will  be  found 
necessary  to  add  a  few  cubic  centimeters  of  hydrochloric 
acid  to  the  water  while  evaporating,  in  order  to  facilitate 
the  solution  of  the  iron.  This  should  be  done  on  a  separate 
portion  from  that  used  for  the  determination  of  total 
solids.  -' 

The  colors  should  be  matched  immediately  after  adding 
the  sulphocyanide,  since  the  color  fades  appreciably  on 
standing.  The  highest  standard  should  not  contain  more 
than  3  c.c.  of  the  iron  solution,  since  the  color  then  becomes 
too  deep  for  accurate  comparison. 

Determination   of  the    Dissolved    Oxygen. 

Method  of  L.  W.  Winkler. "^ 

Collection  of  Samples. — The  samples  are  collected  in 
glass-stoppered  bottles  of  known  capacity,   holding  about 


*  Berichte,  21   {1888),   2843. 


124  AIR,    WATER,    AND    FOOD. 

250  cubic  centimeters.  When  water  is  taken  from  a  faucet 
the  bottle  is  fillxl  by  means  of  a  tube  which  passes  to  the 
bottom  of  the  bottle.  A  considerable  amount  of  water  is 
allowed  to  pass  through  the  bottle  and  overflow  at  the  top. 
It  will  be  almost  impossible  to  obtain  duplicate  samples 
unless  the  bottles  are  filled  at  the  same  time  by  means 
of  a  T  tube,  owing  to  variations  in  pressure  in  the 
pipes. 

In  taking  samples  from  a  stream  or  pond,  a  stopper 
with  two  holes  is  used.  A  tube  passing  through  one  of 
these  holes  is  sunk  in  the  water  to  the  desired  depth,  and 
the  other  is  connected  with  a  larger  bottle  of  at  least  four 
times  the  capacity  of  the  smaller  one,  and  fitted  in  the  same 
way.  From  the  larger  bottle  the  air  is  exhausted  by  the 
lungs  or  by  an  air-pump  until  it  is  nearly  filled  with  water. 
Unless  the  determination  is  to  be  made  at  once,  the  rubber 
stopper  of  the  smaller  bottle  is  quickly  replaced  by  the 
^lass  stopper  so  that  no  air  is  left  in  the  bottle.  The 
temperature  of  the  water  at  the  time  of  sampling  should 
be  noted. 

The  apparatus  which  has  been  used  in  connection  with 
work  in  this  laboratory  for  collecting  samples  at  various 
depths  down  to  75  feet  is  shown  in  outline  in  Fig.  11.  A  gal- 
vanized-iron  can  of  such  size  as  to  hold  one  of  the  gallon  bot- 
tles is  weighted  with  lead  and  provided  with  ears  at  the  top 
for  suspending.  The  bottle,  which  is  securely  wired  in,  is  pro- 
vided with  a  rubber  stopper  carrying  tw^o  brass  tubes,  one 
ending  just  below  the  stopper  and  projecting  for  about  8  or 
9  inches  above  it,  the  other  extending  to  the  bottom  of  the 
bottle  and  connected  by  heavy  rubber  tubing  with  the 
sample  bottle.  This  is  held  by  brass  brackets,  which  are 
fastened  by  means  of  a  wooden  cleat  to  the  side  of  the  can. 
The  neck  of  the  bottle  is  put  into  the  slot  in  the  upper 


water:  analytical  methods. 


125 


bracket  and  then  it  is  firmly  clamped  by  the  thumb-screw 
of  the  lower  one.  The  arrangement  of  tubes  in  the  sample 
bottle  is  obvious.     In  using  the  apparatus  it  is  quickly 


Fig. II. 

lowered  to  the  desired  depth  by  means  of  a  rope  marked  off 
in  feet.  The  water  enters  the  sample  bottle  and  flows 
through  it  into  the  other.  When  the  bubbles  cease  to  rise, 
indicating  that  the  larger  bottle  is  full,  thus  replacing  the 
water  in  the  sample  bottle  a  number  of  times,  the  apparatus 
is  drawn  to  the  surface.  The  temperature  is  read  from  a 
thermometer  fastened  to  the  tube  inside  the  gallon  bottle. 
The  Determination. — Remove  the  stopper  and  add  2  c.c. 
of  manganous  sulphate  solution  with  a  pipette  having  a 
long  capillary  point  reaching  to  the  bottom  of  the  bottle, 
and  in  the  same  way  add  2  c.c.  of  the  solution  of  sodium 
hydroxide  and  potassium  iodide.  Insert  the  glass  stopper, 
leaving  no  bubbles  of  air,  and  mix  the  contents  of  the  bottle. 


126  AIR,    WATER,    AND    FOOD. 

Allow  the  precipitate  to  settle,  and  add  3  c.c.  of  strong 
liydrochloric  acid  with  another  pipette ;  add  also  one  or  two 
small  glass  beads  and  again  insert  the  stopper.  When  the 
"white  portion  of  the  precipitate  is  entirely  dissolved,  pour 
out  a  part  of  the  solution  into  a  flask,  put  back  the  stopper 
and  shake  the  bottle  vigorously.  Then  rinse  out  the  con- 
tents of  the  bottle  into  the  flask  and  titrate  the  liberated 

iodine  with  approximately  —  sodium  thiosulphate  until  the 

color  becomes  a  faint  yellow.  Then  add  starch  solution 
and  titrate  to  the  disappearance  of  the  blue  color.  The 
first  end-point  should  ;be  taken,  as  the  color  will  return  on 
account  of  the  reducing  action  of  the  organic  matter  present. 

pXYGEN  DISSOLVED. 

From  Report  go  Standard  Methods. 

Sulphuric  Acid. — Specific  gravity  1.4  (dilution  1:1). 

Sodium  Thiosulphate  Solution. — Dissolve  6.2  grams  of 

chemically  pure  recrystallized  sodium  thiosulphate  in  one 

.      .  N 

^liter  of  distilled  water.     This  gives  an  —  solution,  each  c.c. 

of  which  is  equivalent  to  .0002  gram  of  oxygen  or  .1395  ^•^• 

of  oxygen  at  0°  C.  and  760  mm.  pressure.      Inasmuch  as 

this   solution  is  not  permanent,  it  should  be  standardized 

N 
occasionally  against  an  —  solution  of  potassium  bichromate 

40 

as  described' in  almost  any  work  on  volumetric  analysis. 
The  keeping  qualities  of  the  thiosulphate  solution  are  im- 
proved by  adding  to  each  liter  5  c.c.  of  chloroform  and  1.5 
grams  of  ammonium  carbonate  before  making  up  to  the 
prescribed  volume. 
'      '*Calcuiatton  of  Results. — The  standard  method  of  ex- 


water:  analytical   methods. 


127 


pressing  results  shall  be  by  parts  per  million  of  oxygen  by 
weight. 

*'It  is  sometimes  convenient  to  know  the  number  of  c.c. 
of  the  gas  per  liter  of  0°  C.  temperature  and  760  mm.  pres- 
sure, and  also  to  know  the  percentage  which  the  amount  of 
gas  present  is  of  the  maximum  amount  capable  of  being 
dissolved  by  distilled  water  at  the  same  temperature  and 
pressure.  All  three  methods  of  calculation  are  therefore 
here  given : 

Oxygen  in  parts  per  million 

o,ooo2N  X  1.000,000     200N 

=  V  =~Y" 

Oxygen  in  c.c.  per  liter 

_  0.1395N  X  1000      139. 5N 
V  =^V 

Oxygen  in  per  cent,  of  saturation 

200N  X  100     2o,oooN 
^      VXO      ^      VO     * 

N 
Where  N  =  number  of  c.c.  of  —  thiosulphate  solution, 

V  =  capacity  of  the  bottle  in  c.c.  less  the  vol- 
ume of  the  manganous  sulphate  and  potas- 
sium iodide  solution  added  {t.  e.,  less  four 
c.c). 

0  =  the  amount  of  oxygen  in  parts  per  million  in 
water  saturated  at  the  same  temperature  and 
pressure." 


'sBi^.^s.^^ 


128 


AIR,    WATER,   AND    FOOD. 


QUANTITIES  OF  DISSOLVED  OXYGEN  IN  PARTS  PER  MILLION  BY 
WEIGHT  IN  WATER  SATURATED  WITH  AIR  AT  THE  TEMPERATURE 
GIVEN. 


Temp.  C. 

Oxygen. 

Temp.  C. 

Oxygen. 

Temp.  C. 

Oxygen. 

Temp,  C. 

Oxygen. 

o 

14.70 

8 

11.86 

16 

9.94 

24 

8-51 

I 

14-28 

9 

11.58 

17 

9-75 

25 

8.35 

2 

13.88 

10 

II. 31 

18 

9-56 

26 

8.19 

3 

13-50 

II 

II   05 

19 

9  37 

27 

8.03 

4 

13   14 

12 

10.80 

20 

9.19 

28 

7.88 

5 

12.80 

13 

10.57      1 

21 

9  01 

29 

7.74 

6 

12.47 

14 

10-35      1 

22 

8.84 

30 

7.60 

7 

12.16 

15 

10.14 

23 

8.67 

Notes. — This  determination  is  a  good  illustration  of  an 
indirect  volumetric  process.  A  precipitate  of  manganous 
hydroxide  is  formed  in  the  bottle  by  the  reaction  of  the 
manganous  sulphate  and  the  sodium  hydroxide.  This  imme- 
diately combines  with  the  oxygen  in  the  water  to  form  a  cer- 
tain amount  of  manganic  hydroxide.  The  hydrochloric  acid 
which  is  added  reacts  with  the  manganic  hydroxide  to  form 
chlorine,  which  in  turn  liberates  iodine  from  the  potassium 
iodide,  the  amount  thus  set  free  depending  primarily  upon 
the  quantity  of  oxygen  dissolved  in  the  water.  The  presence 
of  considerable  amounts  of  organic  matter  or  of  nitrites  in- 
troduces an  error.  In  such  cases  the  method  must  be  modified 
or  a  correction  made.  Details  of  the  method  used  in  such 
cases  are  given  in  the  paper  by  Winkler  previously  cited. 

A  correction  is  made  for  the  volume  of  the  reagents 
added,  but  since  the  precipitated  hydroxides  had  settled 
before  the  acid  was  added,  no  allowance  should  be  made  for 
the  amount  of  acid,  since  the  water  it  displaces  contains 
neither  oxygen  nor  iodine. 


water:  analytical  methods.  129* 

is  a  constant  for  any  particular  bottle,  and  its  logarithm 
may  be  recorded  in  a  note-book  or  upon  the  bottle  itself. 

If  water  is  collected  in  the  ordinary  way  and  transferred 
to  the  apparatus  by  pouring,  there  will  inevitably  be  an  ab- 
sorption of  oxygen  unless  the  water  is  already  saturated. 
Thus  a  process  w^hich  gives  excellent  results  when  the  water 
is  nearly  or  quite  saturated  may  fail  entirely  to  give  accurate 
results  when  the  dissolved  oxygen  is  low  or  absent.  The 
water  may  be  supersaturated  with  oxygen,  in  which  case  the 
per  cent,  of  saturation  may  be  more  than  one  hundred.* 

Determinations  of  dissolved  oxygen  in  ponds  and 
streams  are  best  made  on  the  spot,  or  at  least  the  re- 
agents should  be  added.  The  very  simple  apparatus  re- 
quired for  the  Winkler  process  can  be  packed  in  small  space, 
and  the  entire  determination  requires  only  a  few  minutes. 
The  absorption  of  the  oxygen  by  the  manganous  hydroxide 
is  complete  almost  at  once,  and  it  is  unnecessary  to  allow  it 
to  settle  for  a  long  time  before  adding  the  acid.  The  titra- 
tion can  be  made  with  a  small  burette  or  pipette  with  accurate 
results. 

Determination  of  Free  Carbonic  Acid.— Reagent. —Stdind- 

N 
ard  —  solution  of  sodium  carbonate.     Dissolve  2.41  grams  of 
22 

dry  sodium  carbonate  in  one  liter  of  distilled  water  which  has 

been  freed  from  carbonic  acid  by  cautious  addition  of  dilute 

solution  of  sodium  carbonate.     Add  5  c.c.  of  phenolphthalein 

indicator   (7  grams   in   a  liter)  to  the   distilled  water  before 

neutralizing  and  measuring.     Preserve  this  solution  in  bottles 

of  resistant  glass,  protected  from  the  air  by  tubes  filled  with 

soda  lime.     One  c.c.  equals  o.ooi  gram  of  CO2. 

*Gill:  Tech.  Quart.,  5  (1892),  250. 


130  AIR,   WATER,    AND    FOOD. 

Procedure. — Measure  100  c.c.  of  the  sample  into  a  tall, 
narrow  vessel,  preferably  a  100  c.c.  Nessler  tube,  and  titrate 

N 

rapidly  with  the  —  sodium  carbonate  solution,  stirring  gently 

until  a  faint  but  permanent  pink  color  is  produced. 

N 

The  number  of  c.c.  of  —  sodium  carbonate  solution  used  in 
22 

titrating  100  c.c.  of  water,  multiplied  by  10,  gives  the  parts  per 

million  of  free  carbonic  acid  as  CO 2. 

Owing  to  the  ease  with  which  free  carbonic  acid  escapes 
from  water,  particularly  when  present  in  considerable  quanti- 
ties, it  is  highly  desirable  that  a  special  sample  should  be 
collected  for  this  determination,  which  should  preferably  be 
made  on  the  ground.  If  the  analysis  cannot  be  made  on  the 
spot,  approximate  results  from  water  not  high  in  free  carbonic 
acid  may  be  obtained  from  samples  collected  in  bottles  which 
are  completely  filled  so  as  to  leave  no  air  space  under  the 
stopper. 

Notes. — The  reaction  consists  in  the  formation  of  acid 
sodium  carbonate: 


NasCOa  +H2O  +CO2  =  2NaHC03. 

The  acid  carbonate  does  not  give  a  pink  color  with  phenol- 
phthalein. 

Determination  of  the  Color.— The  amount  of  color  is 
generally  determined  by  direct  comparison  of  the  water  with 
some  definite  standard  of  color.  Various  standards  of  color 
have  been  proposed,  the  objection  to  most  of  them  being 
that  they  are  not  sufficiently  general  in  their  application, 
being  adapted  only  for  the  color  of  some  particular  class  of 
waters. 


water:  analytical  methods. 


T31 


Nesslerized  Ammonia  Standards. — The  yellowish-brown 
tint  of  the  surface-waters  of  the  Atlantic  watershed  corre- 
sponds, except  in  the  lowest  grades,  very  closely  to  that  of 
nesslerized  ammonia,  so  that  the  standards  for  reading 
ammonia  can  be  used  also  for  the  determination  of  the 
color.  The  comparison  is  made  in  the  same  kind  of  50-c.c. 
tubes  that  are  used  for  the  ammonia  determinations,  but 
the  tubes  used  for  this  purpose  are  kept  separate  from  those 
used  for  the  ammonia,  since  the  least  amount  of  alkali  re- 
maining in  a  tube  (from  imperfect  washing,  for  instance) 
alters  the  color  of  the  water.  The  scale  used  corresponds 
quite  closely  with  the  amount  of  the  standard  ammonium 
•chloride  solution  in  the  standards.  Thus  a  color  of  i.o  is 
nearly  the  same  as  that  produced  by  the  nesslerization  of  i 
-c.c.  of  the  standard  ammonia;  c.i  is  about  the  color  pro- 
duced with  0.1  c.c.  of  the  ammonia  solution.  In  the  higher 
grades  of  color,  above  i.o  or  2.0,  the  tint  varies  considerably 
from  that  of  the  nesslerized  ammonia,  and  the  degree  of 
color  is  then  better  determined  in  wider  tubes  and  in  less 
depth. 

The  degree  of  correspondence  of  the  ammonia  standards 
with  the  natural  waters  is  dependent  largely  upon  the  sensi- 
tiveness of  the  Nessler's  reagent,  a  solution  which  is  so  sen- 
sitive as  to  precipitate  in  two  hours,  matching  the  colors 
m.orc  closely  than  one  which  will  remain  for  twenty- four 
hours.  This  is  perhaps  due  to  the  reddish  tinge  given  to  the 
solution  by  the  incipient  precipitation  of  the  mercuric 
iodide. 

Natural  Water  Standards. — To  avoid  these  variations  in 
color,  standards  made  from  dark-colored  water  from  swamps 
by  various  degrees  of  dilution,  and  verified  by  direct  com- 
parison  with    suitably  prepared    nesslerized   ammonia  stand- 


132  AIR,  WATER,    AND    FOOD. 

ards,  are  used.  They  have  the  same  hue  as  the  waters  to  be 
matched,  as  well  as  a  degree  of  turbidity  which  corresponds 
well  with  that  of  surface-waters  ;  once  prepared,  they  wilt 
keep  for  a  fairly  long  time  if  protected  from  the  light  and 
from  the  dust.  These  are  the  standards  that  are  in  use  in 
this  laboratory.  They  are  periodically  standardized  by 
comparison  with  the  permanent  glasses  of  a  Lovibond 
Tintometer. 

Platinum  Standards. — For  ground-waters  which  have 
only  very  little  color  and  considerable  hardness,  and  for  fil- 
tered waters,  the  platinum  color  standards  are  convenient.* 
According  to  this  scale,  the  color  of  a  water  is  the  amount  of 
platinum  in  parts  per  ten  thousand,  which,  together  with 
enough  cobalt  to  match  the  tint,  must  be  dissolved  to  pro- 
duce an  equal  color  in  distilled  water.  In  practice,  a  stand- 
ard having  a  color  of  5.00  is  prepared  by  dissolving  1.246 
grams  of  potassium  platinic  chloride  (equivalent  to  .5  gram 
platinum),  i.ooo  gram  of  cobalt  chloride  (equivalent  to  .25, 
gram  cobalt),  and  100  c.c.  of  strong  hydrochloric  acid  in  dis- 
tilled water  and  diluting  to  one  liter. 

Dilute  standards  for  use  are  made  by  diluting  varying- 
amounts  of  this  standard  to  50  c.c.  with  distilled  water.  Thus,, 
by  diluting  i  c.c,  2  c.c,  and  3  c.c.  to  50  c.c,  colors  of  o.i,  0.2, 
and  0.3  are  obtained.  It  is  claimed  that  the  platinum  stand- 
ards are  permanent  if  protected  from  the  dust. 

Iodine  Standards. — A  standard  for  color  which  could  be 
made  up  at  the  moment  when  wanted  and  without  the  use  of 
costly  apparatus  would  be  a  desideratum.  Experiments  made 
in  this  laboratory  indicate  that  an  aqueous  solution  containing^ 
a  definite  weight  of  iodine  ofTers  the  best  solution  of  the  prob- 
lem. Owing,  however,  to  the  volatility  of  iodine  even  in 
dilute  aqueous  solution  it  is  better  to  liberate  it  directly  in 

*  Hazen  :  ^4fn.  Chem.  J.,  14  {jSq2),  300. 


water:   analytical  methods.  133 

the  comparison-tube  itself.  For  this  the  following  solutions 
are  required:  Potassium  iodide,  o. i  gram  per  liter;  potas- 
sium bichromate,  0.09  gram  per  liter;  picric  acid,  0.2  gram 
per  liter. 

For  a  color  of  5.0,  50  c.c.  each  of  the  iodide  and  of  the 
bichromate  solutions  are  used;  for  lower  colors  proportional 
amounts  are  taken  and  diluted  to  100  c.c.  with  distilled  water. 
To  each  tube  is  added  i  c.c.  of  the  picric  acid  solution,  and 
just  before  the  colors  are  to  be  matched  add  2  c.c.  of  strong 
sulphuric  acid.  The  color  develops,  as  in  the  case  of  nessler- 
ized  ammonia,  within  ten  minutes  and  can  be  relied  upon 
for  about  half  an  hour.  A  very  slight  milkiness  aids  in  match- 
ing the  color;  a  great  hindrance  to  the  use  of  metallic  solu- 
tions being  their  clearness  or  brightness  as  compared  with 
natural  waters. 

The  comparison-tubes  which  give  the  most  satisfactory 
results  with  colors  from  5.0  to  0.5  on  the  natural  water  scale 
are  ^^/iq  inch  wide  and  9V4  inches  high  to  the  loo-c.c.  mark, 
For  lower  colors,  narrower  tubes,  ^Vie  i^ch  diameter  and  the 
same  depth,  give  closer  readings. 

Determination  of  the  Odor. — Cold. — Shake  violently 
the  sample  in  one  of  the  large  collecting-bottles  when  it  is 
about  half  or  two-thirds  full,  then  remove  the  stopper  and 
quickly  put  the  nose  to  the  mouth  of  the  bottle.  Note  the 
character  and  degree  of  intensity  of  the  odor,  if  any.  An 
odor  can  often  be  detected  in  this  way  which  would  be  en- 
tirely inappreciable  if  the  water  were  poured  into  a  tumbler. 

Hot. — Pour  into  a  beaker  about  five  inches  high  enough 
water  to  one-third  fill  it.  Cover  the  beaker  with  a  well-fitting 
watch-glass  and  place  it  on  an  iron  plate  which  has  been  pre- 
viously heated,  so  that  the  water  shall  quickly  come  to  a  boil. 
When  the  air-bubbles  have  all  been  driven  off  and  the  water 
is  about  to  boil,  take  the  beaker  from  the  plate  and  allow  it 
to  cool  for  about  five  minutes.     Then  shake  it  with  a  rotary 


134  AIR,    WATER,    AND    FOOD. 

movement,  slip  the  watch-glass  to  one  side  and  put  the  nose 
into  the  beaker.  Note  the  odor  as  before.  The  odor  may  or 
may  not  be  the  same  as  that  of  the  water  when  cold;  it  can 
be  perceived,  as  a  rule,  for  only  an  instant. 

Notes. — It  is  inevitable  that  a  certain  personal  equation 
should  influence  this  test.  Each  laboratory  will  have  its  own 
5tandards  for  routine  work,  but  a  certain  familiarity  with  the 
more  common  odors  will  tend  to  allay  public  anxiety  and  to 
aid  in  a  more  watchful  habit  on  the  part  of  consumers.  Good 
ground-waters  do  not  give  distinct  odors  unless  they  are  de- 
rived from  clayey  soil,  but  the  odor  often  betrays  a  contami- 
nated well  more  surely  than  any  other  test.  Surface-waters 
will  nearly  always  yield  a  characteristic  odor.  This  odor  may 
be  due  to  the  organic  matter  contained  in  the  water,  or  to 
the  presence  of  minute  plants  or  animal  organisms. 

Among  the  odors  which  are  frequently  met  are  the 
''  earthy,"  "  vegetable,"  ''  musty,"  "  mouldy,"  "  disagree- 
able," and  "  offensive."  The  "  earthy  "  odor  is  that  of 
freshly  turned  clayey  soil.  "  \^egetable  "  is  the  odor  of 
many  normal  colored  surface-waters;  it  may  be  described 
as  swampy  or  marshy,  pond-like,  and  is  often  strengthened 
by  heating.  "  Musty  "  can  be  likened  to  the  odor  of  damp 
straw  from  stables;  it  is  fairly  characteristic  of  sewage  con- 
tamination, and  by  the  trained  observer  is  distinctly  distin- 
guishable from  the  mouldy  odor.  ''  ]\Iouldy  "  is  the  odor  of 
upturned  garden  or  forest  mould,  or  of  a  moist  hot-house; 
it  is  somewhat  allied  to  the  earthy  odor.  "  Disagreeable  " 
is  a  term  which  is  capable  of  wide  variation  among  different 
observers.  It  may  include  certain  characteristic  odors  which 
are  peculiar  to  the  growth  or  decay  of  certain  organisms,  as 
the  "  pigpen  "  odor  of  Anabccna,  the  "  fishy  "  or  '*  cucum- 
ber "  odor  of  Synura,  etc.  The  term  ''  offensive  "  is  generally 
reserved  for  the  sewages.  These  terms  can  be  taken  only  as 
broad  illustrations  of  the  character  of  the  particular  odor. 


WATER   ANALVTICAL  METHODS.  I35 

since  the  odor  will  very  likely  be  described  by  different  per- 
sons in  different  ways,  and  each  laboratory  will  have  its  own 
characterization.  The  odor  which  often  accompanies  an 
abundant  development  of  diatoms  is  a  good  illustration  of 
this.  It  will  be  called  by  various  inexperienced  observers 
offensive,  rotten,  fishy,  geranium-like,  aromatic,  in  one  and 
the  same  sample  of  water. 

The  terms  generally  used  to  signify  the  degree  of  inten- 
sity of  the  odor  are  *'  very  faint,"  ''  faint,"  ''  distinct,"  and 
"  decided."  The  exact  value  to  be  placed  on  each  of  these 
terms  will,  as  a  matter  of  course,  vary  with  the  individual 
analyst,  but  in  a  general  way  it  may  be  said  that  the  ''  very 
faint  "  odor  is  one  that  would  not  be  detected  except  by  the 
trained  observer;  the  ''  faint  "  odor  would  be  recognized  by 
the  ordinary  consumer  if  his  attention  were  called  to  it;  the 
"  distinct  "  odor  is  one  that  would  be  readily  noticed  by  the 
average  consumer,  but  would  not  interfere  with  the  use  of 
the  water;  while  the  "  decided  "  odor  is  one  which  would,  in 
all  probability,  render  the  use  of  the  water  unpleasant. 

Biological  Examination — The  close  relation  of  the  odor 
to  the  living  fauna  and  flora  of  the  water  makes  it  desirable 
that  the  chemist  shall  be  able  to  recognize  the  more  common 
forms  of  water  plants  and  animals  even  if  he  makes  no  pre- 
tensions to  a  knowledge  of  cryptogamic  botany  or  of  zo- 
ology. Therefore  a  microscope  and  a  concentration  appara- 
tus should  be  in  every  water-laboratory.  A  full  description 
will  be  found  in  Whipple.''' 

The  bacteriological  examination  belongs  to  the  expert 
rather  than  to  the  student,  certainly  in  the  present  state  of 
our  knowledge  of  the  lower  organisms.  It  may  be  desirable 
for  the  student  to  be  familiar  with  the  simpler  methods  of 
plate  and  tube  culture,  and  the  water-works  laboratory 
should,  as  in  the  above  case,  be  provided  with  means  for  plain 

*  "  Microscopy  of  Drinking-water."     2d  ed.     N.  Y,,  Wiley. 


136  AIR,    WATER;    AND   FOOD. 

number  counts,  and  directions  for  avoidirj  errors  due  to 
variations  in  temperature,  time  of  culture,  etc.,  consult 
Frankland's  "Micro-organisms  in  Water";  *' Manual  of 
Bacteriology,"  Muir  and  Ritchie;  ''Water  Bacteriology," 
Prescott  and  Winslow. 

Determination  of  the  Turbidity  and  Sediment. — The 
suspended  matter  remaining  in  the  water  after  it  has  rested 
quietly  in  the  collecting-bottle  for  twelve  hours,  or  more,  is 
called  its  turbidity,  and  that  which  has  settled  to  the  bottom 
of  the  bottle,  its  sediment. 

Good  ground-waters  are  often  entirely  free  from  turbidity 
and  sediment,  the  suspended  matters  having  been  filtered  out 
during  the  subterranean  passage  of  the  water,  but  this  is 
rarely  true  of  surface-waters.  The  turbidity  is  various  in 
character  and  amount,  sometimes  milky  from  clay  or  ferrous 
iron  in  solution;  usually  it  consists  of  fine  particles,  generally 
living  algae  or  infusoria.  These  often  collect  on  the  side 
toward  or  from  the  light,  and  a  practised  eye  can,  not  infre- 
quently, recognize  their  forms.  Some  of  the  lower  animal 
forms  can  also  be  seen  by  the  naked  eye,  and  the  larger  En- 
tomostraca  are  quite  noticeable  in  many  waters. 

The  sediment  may  be  earthy  or  flocculent;  in  the  latter 
case  it  is  generally  debris  of  organic  matter  of  various  kinds. 
The  degree  of  turbidity  is  expressed  by  the  terms  "  very 
slight,"  ''  slight,"  "  distinct,"  and  '*  decided,"  and  the  degree 
of  sediment  by  *'  very  slight,"  ''  slight,"  "  considerable,"  and 
"  heavy."  These  determinations,  again,  are  of  value  only  to 
the  routine  worker,  and  for  him  there  are  various  methods  in 
use.  The  papers  of  Parmelee  and  Ellms  ^  and  of  Whipple 
and  Jackson  j  should  be  consulted  for  a  description  of  these. 

Permanent  standards,  however  desirable  for  a  routine 
laboratory  where  many  samples  are  tested  daily,  are  not 
very  reliable  for  students'  work  where  the  tests  are  made 

*  Tech   Quart.,  12  {18 gg),  145.  '\Ibid.,  283. 


watkr:  analytical  methods.  137 

only  at  intervals  and  for  educational  rather  than  technical 
purposes. 

Determination  of  Alum. — On  account  of  the  use  of  alum 

or  aluminum  sulphate  as  a  coagulant  in  the  filtration  of 
water,  a  determination  of  alumina  in  the  effluent  water  is 
often  necessary.  This  may  be  readily  made  by  the  log- 
wood test.* 

Directions. — The  logwood  solution  is  made  as  follows: 
Take  two  grams  of  logwood  chips  and  boil  one  minute  in  a 
platinum  dish  with  50  c.c.  of  distilled  water.  Decant  the 
solution  and  boil  again  for  one  minute  with  50  c.c.  of  water. 
Decant  this  and  similarly  boil  a  third  time  with  50  c.c.  of 
water.  Decant  this  into  a  platinum  receptacle  for  use. 
Take  three  drops  for  each  test.  Kept  in  platinum,  the  solu- 
tion will  last  for  several  days  at  least. 

Test  the  water  as  follows:  Boil  50  c.c.  of  the  water  in 
a  platinum  dish  for  a  short  time  to  expel  carbon  dioxide. 
Add  three  drops  of  the  logwood  solution  and  continue  boiling 
for  a  few  seconds  to  develop  the  color.  Decant  into  a  glass 
flask  and  cool  quickly  under  the  tap  (so  as  not  to  keep  the 
hot  solution  too  long  in  the  glass).  Transfer  to  a  No.  2 
beaker  and  blow  in  carbon  dioxide  from  the  breath  by  means 
of  a  glass  tube  until  there  is  no  further  decolorization.  Pour 
the  water  into  a  Nessler  tube  for  comparison  with  standards 
similarly  prepared.  Allow  them  to  stand  several  hours 
before  taking  the  final  reading.  No  wash -water  is  used  at 
any  of  the  decantations.  The  test  shows  one  part  of 
aluminum  sulphate  in   8,000,000  parts  of  w^ater. 

A  blank  made  with  distilled  water,  if  not  completely 
decolorized  by  the  CO2,  will  show  a  tint  perceptibly  fainter 


*  E.  H.  Richards:    Tech.  Quart.,   4  {i8gi),  194.      A.  H.  Low,    Tech.  Quart., 
15  {1902),  351. 


I3»  AIR,    WATER,    AND    FOOD. 

than  that  produced  by  one  part  in  8,000,000  of  aluminum 
sulphate. 

It  should  be  noted  that  carbon  dioxide  must  be  kept 
absent  until  the  point  prescribed.  The  solution  is  therefore 
transferred  to  a  beaker  in  order  to  keep  the  flask  free  from 
carbon  dioxide  for  the  next  test. 

The  main  points  are: 

1.  Any  kind  of  logwood  appears  to  answer. 

2.  The  solution  is  good  for  several  days,  at  least,  if  kept 
in  platinum. 

3.  The  use  of  platinum  instead  of  glass  for  boiling  the  test. 

4.  The  use  of  carbon  dioxide  instead  of  acetic  acid. 
Aluminum  hydrate,  as  pointed  out  by  the  late  Professor 

A.  R.  Leeds  in  1893,  wdll  produce  a  tint  almost  as  strong  as 
if  it  were  in  solution,  but  of  a  distinctly  differing  tint. 

Mr.  Low's  method  of  procedure  is  as  follows:  First, 
test  the  water  as  above  described.  If  no  tint,  or  none  ex- 
ceeding that  of  the  blank,  remains  after  standing  several 
hours  or  over  night,  that  is  sufficient.  If,  however,  a  tint 
persists,  or  a  colored  precipitate  settles  out,  it  is  necessary 
to  determine  if  this  is  due  to  aluminum  hydrate.  Pour  a 
sample  of  the  water  several  times  through  a  double  Swedish 
filter,  and  finally  test  the  filtrate.  If  the  tint  produced  is 
weaker  than  that  given  by  the  unfiltered  water,  repeat  the 
operation  on  a  fresh  portion  of  the  water,  using  the  same 
filter,  and  continue  repeating  with  new  portions  of  the 
water  and  always  using  the  same  filter,  until  it  is  apparent 
that  no  further  diminution  of  the  tint  can  be  effected. 

For  a  less  delicate  test  in  school  laboratories  where 
platinum  is  not  available,  the  following  alternative  method 
may  be  used: 

Dissolve  about  o.i  gram  pure  haematoxylin  in  25  c.c. 
water ;  this  solution  will  keep  for  two  weeks  and  works  best 


watp:r:  analytical  methods.  139 

after  being  made  several  hours.  To  50  c.c.  of  the  water, 
placed  in  a  four-inch  porcelain  dish,  add  two  drops  of  the 
haematoxylin  solution,  allow  the  solution  to  stand  for  one 
or  two  minutes,  then  add  a  drop  of  20  per  cent,  acetic  acid. 
The  standards  are  prepared  at  the  same  time,  using  50  c.c- 
of  distilled  water  and  the  required  amount  of  a  stand- 
ard alum  solution.  The  comparison  must  be  made  imme- 
diately, since  the  color  fades  on  standing.  In  this  way  the 
presence  of  one  part  of  aluminum  sulphate  in  five  million  can 
be  determined  directly  in  the  water  and  with  ease. 

Logwood  may  be  used  instead  of  the  haematoxylin,  the 
solution  being  prepared  as  above. 

Notes. — This  test  will  show  the  presence  of  all  soluble  salts 
of  aluminum  which  enter  into  combination  with  the  coloring 
matter  of  the  logwood  to  form  a  "  lake." 

The  alkalies  and  alkaline  earths  give  a  purplish  color  with 
logwood  extract,  hence  the  test  for  alum  can  be  made  only  in 
acid  solution. 

Determination  of  Lead. — Lead  in  the  minute  quantities 
in  which  it  ordinarily  occurs  in  water  is  best  estimated  by 
comparing  the  color  of  the  sulphide  with  standards. 

Directions. — If  the  water  is  colorless,  acidify  the  clear  solu- 
tion, concentrated  if  need  be,  with  tw^o  or  three  drops  of 
acetic  acid,  and  pass  in  hydrogen  sulphide  to  saturation.  If 
a  color  is  produced,  compare  it  in  a  loo-c.c.  tube  with  the 
color  given  by  varying  quantities  of  a  standard  lead  solution. 

If  the  water  is  too  highly  colored  to  estimate  the  lead  di- 
rectly, evaporate  three  or  four  liters  in  a  porcelain  dish  to 
about  25  c.c,  add  10  c.c.  of  ammonium  chloride  solution  and 
a  considerable  excess  of  strong  ammonia.  Then  add  hydro- 
gen sulphide  water  and  allow  the  dish  to  stand  some  hours. 
Boil  the  contents  of  the  dish  for  a  few  moments  to  expel  the 


I40  AIR,    WATER,    ANT>    FOOD. 

excess  of  hydrogen  sulphide,  and  fiUer.  The  precipitate  con- 
tains all  the  lead,  iron,  and  suspended  organic  matter,  also 
copper  and  zinc  if  present,  while  the  soluble  color  goes  into 
the  filtrate.  Wash  once  with  hot  water,  transfer  the  filter  to 
the  original  dish,  and  dissolve  the  sulphides  by  boiling  with 
■dilute  nitric  acid  (i  part  acid,  sp.  gr.  1.2,  to  5  parts  water). 
Filter  and  wash;  evaporate  to  10-15  c-c,  cool,  add  5  c.c.  con- 
centrated sulphuric  acid  and  evaporate  until  copious  fumes 
are  given  ofif.  Then,  if  the  original  water  contained  less  than 
0.25  part  iron  per  million,  add  acetic  acid  and  ammonia,  boil, 
filter,  and  read  the  amount  of  lead  in  the  alkaline  filtrate, 
making  the  standards  (page  260)  also  alkaline  with  ammonia. 

If  the  water  contained  over  .25  part  iron,  wash  the  lead 
sulphate  into  a  beaker  with  alcohol  and  water,  and  let  it  set- 
tle overnight.  Filter,  wash  free  from  iron  with  50  per  cent, 
alcohol,  dissolve  the  precipitate  by  boiling  with  ammonium 
acetate,  filter,  and  determine  the  lead  as  above. 

Note. — If  more  than  .25  part  of  iron  is  present,  some  of 
the  lead  will  be  held  by  the  precipitated  ferric  hydroxide;  and 
if  25  parts  are  present,  all  of  the  lead  may  be  lost  in  this  way; 
hence  the  modification  of  the  method  in  the  presence  of  con- 
siderable quantities  of  iron.* 

When  copper  is  also  present  it  is  detected  by  the  blue 
color  given  to  the  ammoniacal  filtrate  from  the  iron  precipi- 
tation. 

Statement  of  Results. — In  reporting  water  analyses  the 
results  are  best  expressed  in  milligrams  per  liter,  which  for 
the  majority  of  waters  is  equivalent  to  "  parts  per  million." 
Occasionally  it  may  be  desirable  to  express  the  results  in 
"  grains  per  gallon."  Parts  per  million  may  be  converted  into 
grains  per  U.  S.  gallon  by  multiplying  by  0.058.     For  con- 

*  Ann.  Rep.  State  Bd.  Health,  Mass.,  1898,  577. 


water:   analytical  methods. 


141 


venience  the  results  should  be  arranged  in  tabular  form,  such 
an  arrangement  being  suggested  below: 


sanitary  water-analysis. 

(Parts  per  1,000,000.) 


Date. 

Physical.                                i 

Residue  on  Evaporation. 

No. 

Color. 

Turb. 

Sed. 

Odor. 

Total. 

Loss. 

Fixed. 

Change 

Cold. 

Hot. 

Ignition. 

121 
123 

3-9-'oo 

.50 
0.0 
0.0 

Dec. 

None 

Cons. 

None 

None 

F.  Veg. 
None 

42 -5 

64.0 

9740.0 

12.5 

30,0 

(Slight 
\  black 

123 



Nitrogen  as 

No. 

Total 
Organic. 

Alb.  Ammonia. 

Free  Am, 

Nitrite. 

Nitrate. 

Ox. 

Cons. 

Total. 

Sol. 

Susp. 

X2I 
122 

.598 

.306 
.014 
.032 

.170 

.136 

.056 
.000 
.560 

,    -003 
.000 
.003 

.220 
1.40 
1. 14 

4.83 

•41 

3-23 

123 

Hardness 

Chlorine 
as 
Chlo- 
rides. 

Iron. 

Biological  (per  c.c.) 

No. 

Bac. 

Plants. 

Diatoms. 

Cvano- 
phyceae. 

Algae. 

Animals, 

121 
122 

20.0 

23.0 

560.0 

1.8 

6.3 

1198.0 

.01 

.46 



I 

° 

0 

229 

123 

No.  121  is  from  a  pond;  122  from  a  spring;  123  from  an  artesian  well. 


CHAPTER   VIII. 

FOOD  IN  RELATION    TO    HUMAN    LIFE:   COMPOSITION,   SOURCES, 

DIETARIES. 

Life  itself  is  conditioned  on  the  food-supply.  Wholesome  food 
is  a  necessity  for  productive  life.  Man  can  and  does  exist  on  very 
unsuitable,  even  more  or  less  poisonous,  food,  but  it  is  merely 
existence  and  not  effective  life.  This  is  true  not  only  of  the 
wage-earner,  but  of  the  business-man,  the  professional  man,  the 
5icholar.  To  be  well,  to  be  able  to  do  a  day's  work,  is  man's 
birthright.  Nevertheless  a  too  large  proportion  of  the  American 
people  sells  this  most  valuable  possession  for  a  mess  of  pottage 
which  pleases  the  palate  for  three  minutes  and  weights  the  diges- 
tive organs  for  three  hours.  With  the  products  of  the  world  ex- 
posed in  our  markets,  the  restraints  of  a  restricted  choice,  as  well 
as  inherited  instincts  or  traditions,  lose  their  force.  The  buyer, 
unless  he  has  actual  knowledge  to  guide  him,  is  swayed  by  the 
caprices  of  the  moment  or  the  condition  of  his  purse,  and  often 
fails  to  secure  adequate  return  in  nutritive  value  for  the  money 
paid.  The  fact  that  so  much  manipulated  material  is  put  upon 
the  market  renders  this  choice  of  food  doubly  difficult,  since  the 
appearance  of  the  original  article  is  often  entirely  lost,  and  to 
city-bred  buyers  even  the  natural  product  conveys  little  idea  of 
its  money  value.  It  is  now  even  more  necessary  that  an  elemen- 
tary knowledge  of  the  proximate  composition  and  food  value  of 
the    more    common    edible  substances  should  be  recognized  as 

an  essential  part  of  education. 

142 


FOOD    IN    RELATION    TO    HUMAN    LIFE.  1 43 

Food:  Definition  and  Uses. — Food  is  that  which  builds  up  the 
body  and  furnishes  energy  for  its  activities:  that  which  brings 
within  reach  of  the  living  cells  which  form  the  tissues  the  elements 
which  they  need  for  life  and  growth.  Only  such  available  sub- 
s^^ances  can  be  called  food,  no  matter  what  their  chemical  compo- 
sition may  be.  Soft  coal  contains  carbon  and  hydrogen  and  is 
food  for  the  furnace,  but  is  not  available  for  the  animal  body. 

This  food  which  is  taken  into  the  body  is  used  in  various  ways. 
It  forms  and  builds  up  new  tissues,  besides  repairing  and  making 
good  the  waste  of  tissues  due  to  bodily  activity;  it  is  stored  up  in 
the  body  to  meet  a  future  demand;  it  supphes  the  needed  heat 
by  the  transformation  of  its  stored  up  or  potential  energy  into  the 
muscular  energy  required  by  the  body;  it  may  be  used  to  protect 
the  tissues  of  the  body  from  being  themselves  consumed  as  food. 

Composition  of  Food. — We  determine  what  chemical  elements 
enter  into  the  composition  of  the  body  by  an  analysis  of  the  various 
organs  and  tissues.  We  learn  what  combinations  of  these  ele- 
ments serve  as  food  by  determining  those  present  in  mother's  milk 
and  in  foodstuffs  which  experience  has  proved  to  furnish  perfect 
nutrition.  From  these  studies  it  is  apparent  that  about  fifteen 
chemical  elements  are  constant  constituents  of  the  human  body; 
that  about  a  thousand  natural  products  are  known  to  have  food 
value;  that  of  these,  one  hundred  are  of  world-wide  importance 
(see  table,  page  150),  and  that  ten  of  them  form  nine-tenths  of 
the  food  of  the  world. 

The  composition  of  food,  as  shown  by  chemical  analysis,  is 
not,  however,  the  only  factor  that  must  be  known  to  determine  its 
value.  The  digestibility  of  the  material  must  be  taken  into  account 
as  well.  "We  live  not  upon  what  we  eat,  but  upon  what  we  digest." 
It  is  more  important  to  know  the  amount  of  available  nutrients 
than  the  amount  of  total  nutrients. 

Food  Principles. — While  the  foodstuffs  present  great  variety, 
the    food    principles   may    be    grouped    under    four    headings; 


144  AIR,    WATER,    AND   FOOD. 

viz.,  nitrogenous  substances  or  proteids,  fats,  carbohydrates, 
and  mineral  salts.  Each  orroup  contains  many  members  with 
minor  but  often  essential  differences.  To  make  these  sub- 
stances available,  there  is  needed  an  ample  supply  of  air  and 
of  water, — of  water  for  solution  and  circulation,  of  air  for  the 
oxygen  needed  to  liberate  the  stored  energy  of  the  food  in  the 
place  where  it  will  accomplish  its  purpose. 

Nitrogenous  Substances. — Since,  in  some  way  as  yet  un- 
known to  us,  nitrogen  is  essential  to  living  matter,  such  sub- 
stances as  contain  this  element  in  an  available  form  are  of  the 
first  importance.  Some,  as  albumen,  are  so  closely  allied  to 
human  protoplasm  that  probably  they  need  only  to  be  dis- 
solved to  be  at  once  assimilated.  Others,  as  gluten  and  sim- 
ilar vegetable  products,  undergo  a  greater  change;  while  still 
others,  as  gelatine,  have  a  less  profound  but  marked  effect  in 
[protecting  the  tissues  from  waste. 

The  enzymes,  ''  ferments,"  in  part,  of  the  older  nomencla- 
ture, are  also  highly  nitrogenous  substances  present  in  some 
form  in  nearly  all  foodstuffs  of  natural  origin.  The  nearer 
the  composition  of  the  food  approaches  that  of  the  protoplas- 
mic proteid,  presumably  the  greater  its  food  value,  since  each 
cleavage,  each  hydrolysis,  each  step  in  the  breaking  down  of 
the  highly  complex  molecule,  consisting  of  hundreds  of  atoms, 
is  supposed  to  liberate  the  stored  energy.  Therefore  it  is  not  a 
matter  of  indifference  in  what  form  this  essential  is  taken.  So 
little  is  known,  however,  with  scientific  accuracy  that  stu- 
dents will  find  a  fruitful  field  of  research  along  these  lines  of 
investigation.  Also  together  with  this  element,  nitrogen,  go 
others,  in  small  quantity  to  be  sure,  but  evidently  of  great 
value.  Such  are  sulphur,  iron,  phosphorus.  One  difference 
between  the  several  groups  of  proteids  is  seen  in  this  com- 
bination with  the  metallic  elements  which  seems  to  carry  with 
it  certain  effects.     Until  greater  progress  has  been  made  in 


FOOD     IN    RELATION    TO    HUMAN   LIFE.  1 45 

determining  the  availability  in  the  organism  of  the  various- 
known  substances,  we  must  be  content  with  a  wide  margin 
in  the  calculated  quantities  necessary  for  the  daily  efficiency, 
except  in  the  very  few  instances  of  nearly  pure  substances,  as 
white  of  Qgg.  It  is  evident  also  that  the  manner  of  prepara- 
tion and  the  kind  of  mixtures  used  in  food  will  affect  most 
profoundly  so  unstable  and  complex  a  class  of  substances. 
One  thing  is  certain,  that  the  body  cannot  take  nitrogen 
from  that  which  does  not  contain  it.  Therefore  a  cer- 
tain quantity  of  highly  nitrogenous  food  should  form  a 
portion  of  the  daily  supply.  It  is  usually  held  that  the  body 
seems  to  be  sufficiently  nourished  when  the  food  contains 
an  amount  of  digestible  proteid  equivalent  to  about  loo- 
grams  of  dry  albumen  per  day  for  the  average  adult,  although 
recent  work  has  shown  that  this  figure  is  probably  too  high. 
An  excess  appears  to  have  a  stimulating  effect  and  overloads 
the  system  with  the  waste,  since  the  end-products  are  not 
purely  mineralized  substances,  as  are  carbon  dioxide  and 
water  from  the  carbohydrates,  but  are  compounds  of  an  or- 
ganic nature,  as  creatin,  urea,  and  uric  acid,  which  have 
deleterious  effects  when  accumulated  in  the  system.  A  de- 
ficiency of  nitrogen  is  made  good,  to  a  limited  extent,  by  the 
protective  agency  of  the  other  foodstuffs  which  offer  them- 
selves for  all  the  offices  except  the  final  one  of  tissue-building* 
Fats. — For  this  protective  action,  as  well  as  for  many  other 
purposes,  the  fats  are  most  valuable,  and  if  they  occur  in  about 
the  same  proportion  as  do  the  nitrogenous  elements,  the 
needs  of  the  organism  seem  to  be  well  met.  Thus,  in  mother's 
milk,  in  eggs,  and  in  meat  from  active  animals  these  two  are 
in  nearly  equal  proportions,  while  in  the  cereals  the  fat  is  less; 
in  nuts  and  in  meat  from  fattened  animals,  as  a  rule,  it  is 
higher  than  the  nitrogen.  Little  is  known  as  to  the  varying 
food   value   of  these   fats   from   different   sources.      Certain 


146  AIR,    WATER,    AND    FOOD. 

physical  conditions  of  solidity,  melting-point,  etc.,  seem  to 
have  more  influence  than  mere  chemical  composition.  What- 
ever the  source,  it  is  certain  that  the  stored-up  energy  which 
is  to  serve  the  organism  in  cases  of  loss  of  income  from  any 
cause  is  in  the  form  of  fat,  a  form  which  is  not  subject  to  the 
action  of  agents  which  so  readily  decompose  proteids  and 
carbohydrates  and  yet  is  readily  converted  into  available  food 
whenever  called  for.  That  it  is  not  absolutely  necessary  that 
the  food  should  contain  fat  as  such  seems  to  be  proved  by 
experiment,  but  from  the  fact  that  all  nearly  natural  food- 
substances  do  contain  it,  and  that  it  appears  to  be  more 
economical  of  human  energy  to  take  it  from  these  foods  than 
to  manufacture  it  from  the  proteids  and  carbohydrates,  we 
may  safely  assume  fat  to  be  an  essential  of  the  human  dietary. 

That  the  equality  in  amount  of  fat  with  nitrogenous  com- 
pounds is  not  essential  is  proved  by  the  fact  that  the  strong 
draft  animals,  as  horses  and  oxen,  take  food  in  which  the  per 
cent,  of  fat  is  not  more  than  half  as  much  as  of  proteid;  never- 
theless it  is  present  in  the  food  of  all  animals  and  doubtless, 
in  its  turn,  is  protected  by  an  excess  of  the  third  class  of 
foodstuffs,  the  carbohydrates,  characteristic  of  the  vegetable 
kingdom — a  class  which  in  the  final  decomposition  yield  clean 
volatile  products,  water  and  carbon  dioxide,  and  which,  there- 
fore, do  not  clog  the  system  ro  readily  as  do  urea  and  other 
wastes. 

Carbohydrates. — The  number  of  more  or  less  well-defined 
substances  under  this  head  is  legion:  starches  from  scores 
of  plants,  sugars  from  as  many  more,  gums,  pectins,  and 
dextrins,  all  with  a  certain  food  value,  dependent  prob- 
ably upon  the  utilization  of  the  various  mixtures  with 
which  they  are  taken  into  the  alimentary  canal.  These 
foodstuffs  are  very  liable  to  "  fermentation,"  that  is,  to  an 
acid    decomposition    which    prevents    their    absorption    by 


FOOD    IN   RELATION    TO    HUMAN    LIFE.  147 

the  delicate  lining  of  the  walls  of  the  intestines  and  which 
causes  digestive  disturbance.  The  sugars,  which  are  very 
soluble,  and  therefore  liable  to  be  present  in  excess,  are  es- 
pecially subject  to  this  change.  This  class  of  food-substances 
is  found  in  the  diet  of  civilized  man,  free  to  choose,  in  an 
amount  about  equal  to  the  sum  of  the  other  two  classes,  with 
a  tendency  to  less  rather  than  more.  It  may  be  said  that 
sugar  and  fat  increase  over  starch  in  the  diet  of  a  people  of 
imrestricted  choice,  but  it  is  not  certain  that  the  qualities  of 
body  which  make  for  hardihood  and  resistance  to  disease 
are  correspondingly  increased.  There  is,  indeed,  much  evi- 
dence to  show  that  power  of  digesting  vegetable  foods  indi- 
cates a  general  well-being  of  body  conducive  to  long  life.  A 
ready  adaptation  renders  possible  the  changes  of  habitat  re- 
quired by  civilization.  Unless  one  is  to  be  confined  to  a  nar- 
row range  it  is  wise  to  cultivate  a  strength  of  digestion  as 
well  as  a  strength  of  muscle,  and  for  the  best  brain  power  we 
believe  it  to  be  more  essential. 

Mineral  Salts. — The  fourth  class,  mineral  salts,  comes  into 
the  food  largely  from  the  vegetable  substances  eaten,  for  in 
these  the  union  is  an  organic  one  readily  assimilated.  As  we 
have  seen,  certain  elements  go  with  the  nitrogenous  portion, 
as,  for  example,  in  gluten  and  its  congeners  are  found  sul- 
phur and  phosphorus.  Potassium,  found  in  barley,  is  a  con- 
stant constituent  of  protoplasm,  while  sodium  is  found  in 
blood-serum.  A  lack  of  vegetable  foods  seems  to  impoverish 
the  blood-corpuscles.  For  children,  a  deficiency  in  lime 
causes  serious  disease.  Sugar,  olive-oil,  corn-starch,  and 
other  prepared  food-substances  cannot  take  the  place  of 
asparagus,  cabbage,  carrots,  etc. 

To  sum  up  briefly,  then,  wu  may  say  that  the  protein  or  nitro- 
genous portion  of  the  food  forms  tissue,  such  as  muscle,  sinew  and 
fat,  and  furnishes  energy  in  the  form  of  heat  and  muscular  strength; 


148  AIR,    WATER,    AND     FOOD. 

the  fats  build  up  fatty  tissue,  but  not  muscle,  and  supply  heat;  the 
carbohydrates  are  changed  into  fat  and  supply  heat.  Another  im- 
portant use  of  the  nutrients  is  to  protect  each  other  from  being  used 
in  the  body.  The  carbohydrates,  especially,  in  this  way  protect 
the  protein,  including  muscle,  etc.,  from  consumption. 

Change  in  Composition  Due  to  Cooking. — The  composition  of 
cooked  food  is  in  general  not  the  same  as  the  raw  material  on  ac- 
count principally  of  chemical  and  physical  changes  brought  about 
by  the  heat  employed  in  the  cooking  process.  The  total  nutrients, 
calculated  on  a  water-free  basis,  may  be  practically  the  same,  but 
the  structure  is  often  quite  different. 

Starch  is  hydrolyzed  and  rendered  soluble  by  heating  in  the 
presence  of  moisture,  and  at  higher  temperatures  it  may  be  con- 
verted into  the  brown,  soluble  dextrin.  The  sugars  are  changed, 
being,  in  the  case  of  sucrose,  partly  converted  into  other  forms, 
such  as  invert  sugar,  by  the  heating,  with  the  help  of  the  organic 
acids  present  in  many  foods.  Some  of  the  proteids  tend  to  become 
less  soluble  through  heating  and  at  higher  temperatures  may  be 
even  partly  decomposed  with  possible  loss  of  food  value. 

Heat  of  Combustion. — Until  a  more  definite  knowledge  of  the 
processes  of  metaboHsm  (the  transformations  of  matter  and  energy 
in  the  animal  organism)  is  obtained  the  potential  energy  of  food  is 
calculated  in  terms  of  mechanical  work — expressed  in  heat-units 
or  calories. 

One  calorie  is  the  amount  of  heat  required  to  raise  the  tempera- 
ture of  one  gram  of  water  one  degree  centigrade.  A  gram  of  fat, 
as  actually  digested  and  oxidized  in  the  body,  affords  enough 
heat  to  raise  the  temperature  of  about  9000  grams  of  water  one 
degree.  In  like  manner  a  gram  of  protein  has  an  energy- 
producing  power  expressed  in  calories  of  about  4000,  and  for 
carbohydrates  the  average  value  is  also  4000. 

Allowance  is  made  in  these  figures  for  the  fact  that  to  digest  com- 
pletely any  part  of  our  food  results  in  a  decrease  of  the  amount  of 


FOOD    IN   RELATION    TO   HUMAN    LIFE.  1 49 

energy  to  be  derived  from  it,  and  this  affects  the  protein  more  than 
it  docs  the  other  two.  It  is  probably  true  that  under  favorable  con- 
ditions the  fat  and  carbohydrates  can  be  completely  utilized  in  the 
body  and  consequently  their  energy-producing  power  can  be  correctly 
estimated  from  their  heat-producing  power  outside  the  body.  In 
the  case  of  protein,  however,  the  digestion  within  the  body  is  never 
so  complete  as  to  furnish  all  the  energy  that  would  be  obtained  by 
a  complete  combustion  of  these  nitrogenous  materials  outside  of 
the  body. 

The  fact  remains,  however,  that  all  experiments  yet  made  go 
to  show  that  within  practical  limits  we  are  safe  in  using  the  heat 
of  combustion  (expressed  in  calories)  of  any  food-substance  at  a 
controlling  measure  of  food  values. 

Nutritive  Ratio. — The  requisite  number  of  calories  must,  how- 
ever, be  obtained  by  the  utilization  of  such  substances  as  contain 
all  the  elements  needed  by  the  body,  and  in  such  ratio  as  has  been 
found  available  for  the  balance  of  nutrition.  In  carrying  on  its 
multifarious  activities  the  body  loses  about  20  grams  of  nitrogen 
per  day,  which  must  be  replaced  by  the  same  element  in  the  food 
taken.  Thus  while  the  requisite  number  of  calories  may  be  fur- 
nished by  fat  or  starch,  these  substances  alone  will  not  suffice  for 
complete  nutrition.  The  nutritive  ratio,  or  the  proportion  of 
nitrogeneous  to  non-nitrogenous  food,  must  be  maintained  in  the 
proportion  of  i  to  3,  or  at  least  i  to  5. 

The  following  table  of  one  hundred  common  food-mate- 
rials is  arranged  in  the  order  of  calorific  or  energy-giving 
pov^er,  but  in  considering  the  food  value  of  any  one  substance 
its  nitrogen  content  must  also  be  considered,  and  such  com- 
binations made  as  will  yield  the  requisite  elements  for  a  well- 
balanced  ration. 

From  even  a  cursory  examination  of  the  table  it  will  be 
seen  how  widely  some  of  the  foodstuffs  differ  under  differing 
conditions  of  soil  moisture,  fertilization  in  the  case  of  plants, 


3  =;o 


AIR,   WATER,    AND   FOOD. 


COMPOSITION    OF    SOME    COMMON    FOOD-MATERIALS    AS    PURCHASED. 
I.   Fuel  Value  3000-4000  Calories*  per  Pound. 


Food-material. 


Butter 

Lard  (refined) 

Oleomargarine 

Salt  fat  pork 

Suet 

Walnuts  (shelled) 


Refuse. 


Per  cent. 


Water. 


Nitroge- 
nous 
(Substances. 


Per  cent.        Per  cent. 


0.3  10  12.2 

4.3  lo  21  9 

2-5 


Per  cent. 

85.0 
100.00 

83.0 
80.3  10  94.1 
70  7  to  94.5 

63.4 


II.  Fuel  Value  2000-3000  Calories  per  Pound. 


Bacon     

Cheese  (American  pale). 

Chocolate 

Doughnuts 

Mutton  tlank  (fat) 

Peanut  butter 

Sausage  (farmer) 


18. 4 

31.6 

1.5  10  10.3 

[1  o  to  25.8 

28.9 

2. 1 

22.2 


28.8 
[2.5  10  13.4 
5.1  to  7.6 

10.7 

29  3 

27.9 


59-4         I 

35-9  I 
47.1  to  50.2 
16.4  to  25.7 

59-8 

46.5 

40.4 


III.   Fuel  Value  1500-2000  Calories  per  Pound. 


Barley  (pearled) 

Beans  (dried) 

Cake  avera^'e  (except  fruit). 

Candy.... 

Cheese  (Neuchatel) 

Corn-meal 

Corn-starch         

Crackers  (average) 

Kai  meats 

Gelatin  

Ham  (smoked,  medium  fat) 
Infants'  and  invalids'  foods 

Macaroni 

Oats 

Peanuts 

Peas  (dried) 

Pop-corn 

Rice 


Rye  flour 

Sugar  (cfranulated)   

Wheat  (entire)  flour 

Wheat  flour  (white  bakers'). 

Wheat  (shredded) 

Zwieback 


4.5  to  28.4 


9.8  to  12.9 

9.6  to  15.5 

19-9 

4.0 

42.7  to  57,2 

8.8  to  17.9 
lo.o 

6.8 

38.3 

13.6 
27.3  to  42.5 
2.4  to  12.3 

7.0  to  12.3 

7.8 
6.9 

6.9  to  15.0 

4-3 

9.1  to  14.0 
II. 9  to  13  6 


6.4  to  13.1 

lo.i  to  13.3 

7.2  to  10.7 

5.0  to    7.7 


Including  fibre. 


7.0  to  10. 1 

19.9  to  26.6 

6.3 

15. 1  to  22.3 
6.7  to  11.6 

10.7 
13.0 
84.2 

10.2  to  21.Q 
2.0  to  22.5 
7.9  to  16.6 

16.5 

19-5 
20.4  to  28.0 

10  7 
5.9  to  11.3 
4.9  to    8.8 


12.2  to  14.6 
10.3  to  14.9 
9.6  to  II. 4 
8.6  to  II. 7 


0.7  to  1.5 

I   4  to  3.1 

9.0 

22.3  to  32.5 
1.0  to  5.3 

's  s" 

36.3 

o    I 
24-5  t"  39  9 
0.3  to  10.9 
0.0  to    4.9 

7  3 

29.1 

0.8  to  1.3 

5.0 
0.1  to  0.7 
0.2  to  1.3 


.5    to    2.1 

.9  lo  2.0 
.3  to  1.6 
.1  to  11.3 


26.8  to  33.8 
45.8  to  63.2 


77.3  to  78.1* 
57.2  to  63.5* 

633 

96  o 

2    to    2.9 

68.4  to  80.6* 

90  o* 

71.9* 


66.9  to  89.4 

67.2  to  78.4* 

66.5* 

18.5 

58.0  to  67.4* 

78.7    ^ 

75.4  to  81.9* 
77.6  to  80.2* 

100 

69.5  to  77.0* 

70.3  to  75.5 
75.0  to  79.7* 

72.1  to  74.2 


IV.  Fuel  Value  1000-1500  Calories  per  Pound. 


Apples  (dried)  — 

Bread  (white) 

Corn-bread 

Dates 

Figs 

Fresh  pork  (ribs  and  shoulder). 
Medium  fat  mutton  and  beef.., 

Mince-meat  (commercial) 

Mince-meat  (home-made)   ..    . 

Pies 

Prunes  (dried) 

Raisins 

Sandwiches 

Sardines  (canned)   

Salt  mackerel 


15.0  to  20.3 
14.4  to  27.8 


15  o 
10.0 


5.0 
22.9 


8. 

6  to  47.4 

35-3 

28 

4  10  48.0 

13.8 

II 

.6  to  25.0 

40 

.1  to  4-,.6 

38 

0  to  4^.9 

27.7 

54-4 

44.9 

19.0 

13  I 

44-9 

53  6 

32-5 

6  to  86.91 

53-1 
31054.3 

70.6 
3  to  83.1 


60.2 
32  I 
39.2 
62.2 
68.5 
33-3 


*  One  Calorie  equals  looo  calories. 


FOOD    IN   RELATION    TO   HUMAN    LIFE. 


i5r 


COMPOSITION    OF    SOME    COMMON    FOOD    MATERIALS. —  Continued. 

V.  Fuel  Value  500-1000  Calories  per  Pound. 


Food-material. 


Beef  (round)   

Beef  (sirloin  steak). . 
Chicken  (fowls)   . . . . 

Cream         

Eggs  

Herring  (smoked)   .. 

Meats  (lean)   

Olives   

Salmon  (fresh)   . .    . . 

Salmon  (can  ned> 

Tapioca  pudding. .. 

Tongue  (beef) 

Turkey    . .    

Veal  (breast) 


Refuse. 


Per  cent. 

8.5 

12.8 

18.0  to  42.7 


44.4 
0.5  to  I  1.3 

19.0 
23.8  to  35.-- 
11.7  to  16  9 


9-2  to  55  3 
17.1  to  32.4 
15.7  to  25.4 


Water. 


Per  cent. 

62.5 

54.0 

38  3  to  53.7 

74.0 

65.5 

19.2 

59.9  to  69.2 

52-4 

45.0  to  51 
54.6  to  58 

52.0  to  71 

32.4  to  69 

41. 1  to  44 

48.5  to  55, 


Nitroge- 
nous 
Substances. 


Per  ce.nt. 
19.2 

16.5 

11. 5  to  16.0 

2-5 

11.9 
20.5 

18.1  to  21.4 
1-4 

12.6  to  15.0 
18.6  to  20.2 

2.8  to  4.2 
7.8  to  20.2 
15.8  10  16.8 

14.2  to  16.9 


Fat. 


Per  cent. 

9.2 

16,1 

6.9  to  21.5 


9-3 
8.8 

7.8  to  14.2 
21 .0 

6.6  to  9.5 
5.6  to  9.8 

2.3  to  4.8 
o  7  to  15.3 

5.9  to  25.5 

9.4  to   12.8 


VI.  Fuel  Value  400-500  Calories  per  Pound. 


Beans  (canned  red  kidney). 

Calf's- foot  jelly   

Salt  cod  (boneless) 

Succotash  (canned) 

Sweet  potatoes 


72.7 

77  6 

54.8 

7' 

.4  to  79.9 

55-2 

7.0 

4-3 

27.7 

2.9  to  4.4 

14 


0.3 
0.7  to  1.7 

0.6 


Carbo- 
hydrates. 


Per  cent. 


21.9  to  38. 


18.5 
17  4 


[4.9  to  22.4. 
21.9 


VII.  Fuel  Value  800-400  Calories  per   Pound. 


Bananas  ..  . 
Butter  beans 
Fish  (fresh)   . 

Grapes 

Hash     , 

Milk 

Potatoes  .  -    . 


3-0 
50.0 

!5.2   to  46.0 

25   O 


48.9 
29.4 

46.1  to  49.1 
58.0 
80.3 
87.0 
62.6 


o  8 
4-7 
[1. 9  to  12.0 
i.o 
6.0 
3-3 
1.8 


0.4 

14.3 

0-3 

14.6 

to  5.9 

1.2 

14.4 

19 

9.4 

4.0 

5.0 

0.1 

14.7 

VIII.  Fuel  Value  2^0-300  Calories  per  Pound. 


Apples 

Chicken  (broilers) 

Cranberries 

f)nions   .  .    .. 

Oysters  (solid)   . . . 

Parsnips   ..   

Pears 


25.0 
■4  to  55. 


20.0 
10.0 


63.3 
44.6  to  S2.4 
87.6  10  89.5 

78.9 
82.2  to  92.4 

66.4 

76.0 


0-3 
9.0  to  15.7 
0.4  to  0.5 

1.4 

4.5  to  7.3 
1-3 
0.5 


0-3 
I.I  to  T.8 
0.4  to  0.9 

0-3 

0.5  to  1.8 

0.4 

0.4 


9.3  to  10.9 

8.9 
1.5   to  6.2 

10.8 
12.7 


IX.  Fuel  Value  100-200  Calories  per  Pound. 


Beets.... 
Cabbage 
Carrots 
Green  corn 
Lemons 
Or.^nges 
Soups (canned) 
Spinach 

Squash 

Tomatoes  (canned) 


7D.0 

77  7 

70.6 

29.4 

62.5 

6:5.4 
91.0  to  92.8 
L)i.6  to  92.8 

44  2 

Q2.5   to  07.9 


13 
1.4 
0.9 
I  .2 
07 
0.6 
2.Q    to    5.0 

1.8  to  2.4 

o  7 
0.3  to  17 


to    O 

to  o. 
0.2 


X.   Fuel  Value  10-100  Calories  per  Pound. 


Asparagus 

Bouillon  (canned) 
Celery 
Cucumbers 
Watermelons 


94 

0         1 

96 

51096.7  1 

7S 

6 

81 

I 

37 

5 

.7  to  2 
0.9 
0.7 


7-7 
4.8 
7-4 
7-7 
S  9 
8.5 

to  5.7 
to  3.4 

4.5 

to  8.1 


3-3 

to  0.3 
2.6 
2.6 


152 


AIR,    WATER,    AND    FOOD 


and  of  fatness  or  leanness  in  animals,  of  method  of  prepara- 
tion or  of  combination  in  cooked  foods. 

Therefore  examinations  of  materials  are  imperative  if 
there  is  to  be  any  basis  of  calculation.  In  an  institution  where, 
for  instance,  flour  forms  two-thirds  of  the  daily  ration,  if  it 
contains  the  lowest  per  cent,  of  nitrogen  it  may  not  furnish 
sufficient  proteid  for  a  well-balanced  ration,  or  if  the  meat 
used  is  very  lean  there  may  not  be  fat  enough  for  the  best  nu- 
trition. 

The  great  variation  in  the  proportion  of  water  leads  to 
many  surprises,  and  the  amount  of  unedible  material  is  to  be 
considered.  The  uneducated  provider  buys  oysters  under  the 
impression  that  he  is  furnishing  food  of  high  value,  and  does 
not  distinguish  between  potatoes  and  rice. 

In  the  present  state  of  our  knowledge,  the  best  use  to 
which  we  can  put  such  tables  and  analyses  is  as  a  check 
against  gross  errors  of  diet,  which  are  found  with  alarming 
frequency  especially  among  children  and  students,  those  who 
can  least  afford  to  make  them.  References  will  be  found  in 
the  Bibliography  to  works  for  further  study  along  these  lines. 

Dietaries. — A  dietary  is  simply  a  known  amount  of  food  of 
known  composition  per  person  per  day,  week,  or  month. 

What  is  called  a  standard  dietary  is  such  a  combination  of 
food-materials  as  shall  furnish  the  amounts  held  to  be  neces- 
sary.   The  following  are  examples  of  such  standard  dietaries: 


Approximate  Amounts 
required  daily  by 

Nitroefnous. 
grams. 

Fats, 
grams. 

Carbohydrates, 
grams. 

Calories. 

Child  of  6-g 

62 

78 

100 

100 

125 

45 
45 
75 
90 
125 

200 

281 
380 
450 
500 

1593 
1890 
2665 
3092 
3725 

Adult  at  rest 

Adult  at  moderate  work 
Adult  at  hard  work... 

(In  feeding  experiments  from    10  to  20  per  cent,  more   must  be  allowed 
for  waste  and  indigestibility.) 


FOOD    IN    RELATION    TO    HUMAN    LIFE.  1 53 

From  the  table  on  p.  150  may  be  selected  such  food  as  will 
give  the  required  quantities  in  variety  enough  to  suit  any  taste. 
That  which  the  table  cannot  give  is  the  per  cent,  of  each  which, 
under  any  given  condition,  will  be  utilized  by  the  person  fed. 
The  strength  of  the  digestive  juices,  exercise,  fresh  air,  the 
cooking,  the  mixing  of  the  foods,  the  habits  of  mind  as  to 
food,  the  customs  of  the  family,  all  influence  this  utilization, 
so  that  other  means  must  be  resorted  to  in  order  to  gain  an 
idea  of  what  is  practicable.  This  is  done  by  taking  account 
of  the  food  of  persons  free  to  choose  ;  of  those  in  different 
countries,  in  different  circumstances,  and  using  a  great 
variety  of  materials.  Since  Voit  made  his  standard  dietary  in 
1870,  many  hundreds,  at  least,  have  been  so  gathered  in  the 
United  States  alone — more  than  two  hundred  since  1886.  All 
the  information  thus  gained  goes  to  confirm  the  theoretical 
standard,  and  also  to  show  how  much  depends  upon  suitable 
preparation  and  combination.  These  last  two  things  help 
each  other. 

As  food  is  ordinarily  prepared,  about  10  per  cent,  must 
be  deducted  for  indigestibility  in  a  customary  mixed  diet,  and 
about  10  per  cent,  more  for  the  refuse  or  waste  of  food  as 
purchased,  so  that  of  the  total  pounds  of  meat,  vegetables, 
and  groceries  some  20  per  cent,  is  of  no  final  service  in  the 
body.  It  is  immaterial  whether  this  amount  is  subtracted 
from  the  final  calculation  or  whether  the  higher  figures  be 
taken,  that  is,  whether  125  grams  of  proteid  as  purchased  or 
TOO  grams  final  utility  is  used.  There  will  be  an  unknown 
limit  in  either  case.  According  to  late  experiments  100 
grams  of  proteid  is  high.  The  waste  of  fats  is  less  in  propor- 
tion as  the  dietary  is  a  restricted  one. 

Knowledge  of  Food  Values  Necessary. — The  most  serious 
aspect  of  the  food  question  is  that  the  taking  of  it  is  volun- 
tary, not,  like  air,  a  necessity  beyond  control,  and  that  the 


154  AIR,    WATER,    AND    FOOD. 

most  fantastic  ideas  are  allowed  to  rule.  The  day-laborer  is 
in  little  danger,  since  his  food  demand  is  made  strong  by  out- 
of-door  exercise;  but  the  student  who  shuts  himself  up  in 
hot,  close  rooms,  and  who  does  not  look  upon  food  as  his 
capital,  but  only  as  a  disagreeable  task  or  an  amusement,  is  in 
great  danger,  as  is  he  who,  having  heard  that  one  can  live  on 
a  few  cents  a  day,  proceeds  to  try  it  without  knowledge,  and 
suffers  a  loss  of  efficiency  for  years  or  for  all  his  life. 

It  is  not  nearly  so  difffcult  to  acquire  a  working  knowl- 
edge of  food  values  as  of  whist  or  golf,  so  that  on  entering  a 
restaurant  a  suitable  menu  may  be  made  up  within  one's  al- 
lowance. It  is  only  necessary  to  correct  prevailing  impres- 
sions and  reinforce  one's  experience. 

Figs,  dates,  raisins,  and  prunes  are  apt  to  be  regarded  as 
luxuries  instead  of  as  rich  food-substances  of  a  most  di- 
gestible kind  when  freed  from  skin  and  seed.  Nuts  are  a 
much  neglected  form  of  wholesome  food,  admirably  suited 
to  a  winter  table  from  their  richness  in  fat,  and  also  furnish- 
ing muscular  energy,  as  is  seen  in  the  agile  squirrel,  and  is 
proved  by  many  human  examples.  With  nuts,  however, 
must  be  taken  fruits  or  other  bulky  foods,  to  balance  the  con- 
centration. The  somewhat  compact  and  oily  substance  must 
be  finely  divided  and  freed  from  its  astringent  skin. 

In  distinction  from  these  rich  foodstuffs,  we  find  oranges, 
apples,  etc.;  the  usual  garden  vegetables,  asparagus,  lettuce, 
etc.,  which,  while  they  fill  an  important  place  in  the  dietary, 
add  little  directly  to  the  energy  of  the  body  and  need  not  be 
considered  except  as,  by  their  flavor  or  aesthetic  stimulus, 
they  add  to  the  efficiency  of  the  rest. 

The  foods  which  furnish  the  greatest  nutrition  for  the  least 
money  are  such  materials  as  corn  meal,  wheat  flour,  milk, 
beans,  cheese  and  sugar.  The  expensive  cuts  of  meat,  high- 
priced   breakfast    cereals    and    the    like,  add    but    little    to    the 


FOOD    IN    RELATION    TO    HUMAN    LIFE.  1 55 

nutritive  value  but  greatly  increase  the  cost  of  living.  A  meal  of 
lettuce  dressed  with  oil,  eaten  with  bread  and  cheese,  fulfils  all  the 
requirements  of  nutrition,  and  may  cost  five  cents.  The  same 
food  value  from  sweet  breads,  grape-fruit,  etc.,  might  cost  a  dollar. 
Incorrect  ideas  in  regard  to  food  values,  and  prejudice  inherited  or 
acquired  against  certain  foods,  have  too  often  resulted  in  exclud- 
ing wholesome  and  nutritious  articles  from  the  dietary  and  de- 
creasing thereby  the  efficiency  of  the  human  machine. 


CHAPTER  IX. 

THE  PROBLEM  OF  SAFE  FOOD.     ADULTERATION  AND  SOPHISTICATION. 

Adulteration  grows  largely,  if  not  almost  entirely,  from  exces- 
sive competition.  Nearly  every  article  of  common  food  has  been 
found  at  one  time  or  another  to  be  adulterated,  yet  manufacturers 
testify  that  they  willingly  would  stop  this  addition  of  foreign 
material  if  they  could  be  sure  that  their  competitors  would  stop 
also.  Other  causes  there  are  also :  the  demand  for  goods  out  of 
season;  for  perishable  products  which  must  come  many  miles; 
the  failure  of  the  supply  of  a  given  substance  to  meet  a  continu- 
ing demand;  all  of  these  lead  to  adulteration,  imitation  and  sub- 
stitution. 

To  many  people  otherwise  intelligent,  the  term  adulterated  food 
is  synonymous  with  poisoned  food.  With  others,  thanks  to  alarm- 
ing newspaper  articles,  not  wholly  disinterested,  the  general  im- 
pression is  far  beyond  the  reality.  It  is  not  necessary  to  use  poison- 
ous or  even  deleterious  material :  it  needs  only  to  mix  with  the  food 
material  some  substance  cheaper  but  harmless,  to  make  some 
change  in  the  outward  appearance  of  the  article  so  that  people 
shall  not  recognize  the  familiar  substance,  and  then  to  herald  far 
and  wide  the  discovery  of  a  new  process  by  which  the  food  value 
is  greatly  enhanced.  "Things  are  not  what  they  seem"  is  nowhere 
more  true  than  in  the  case  of  foods. 

Definition  of  Adulteration. — To  adulterate  is  ''to  debase''  "to 
make  impure  by  an  admixture  of  baser  materials."  The  word 
"adulterated  refers  to  any  food  to  which  any  foreign  substance, 
not  a  proper  portion  of  the  food,  has  been  added.     It  does  not 

156 


THE  PROBLEM  OF  SAFE  FOOD.  T^J 

matter  whether  the  added  material  is  of  greater  value  than  the 
food  itself.  The  addition  of  coffee  to  cereal  or  substitute  coffees, 
is  properly  held  to  be  an  adulteration.  Deterioration  should  not 
be  mistaken  for  adulteration.  People  who  are  not  wholly  familiar 
with  the  appearance  of  a  food  or  the  chemical  and  physical  changes 
which  it  may  undergo,  think  that  if  it  does  not  taste  just  right  or 
look  just  right  that  it  must  be  adulterated.  Appearance  has  slight 
relation  to  the  purity  of  the  article  in  these  days  of  paint,  polish 
and  powder. 

Some  forms  of  adulteration  are  more  properly  described  under 
the  head  of  misbranding,  that  is,  referring  to  foods  incorrectly  de- 
scribed by  the  label.  While  the  significance  is  not  exactly  the 
same  as  that  of  the  w^ord  adulterated,  yet  the  two  may  sometimes 
be  apphed  to  the  same  product.  For  instance,  the  addition  of 
starch  to  sausage  to  conceal  the  use  of  excessive  amounts  of  water 
and  of  fat  constitutes  an  adulteration,  which  would  not  be  the  case 
if  the  article  were  properly  branded  to  show  the  presence  of  the 
added  "filler." 

To  adulterate  the  coin  of  the  realm  or  the  liquor  of  the  bar  with 
a  baser  metal  or  an  imitation  whisky  is  a  heinous  offence.  So  is 
the  mixture  of  milk  w^ith  the  baser  article,  water,  which  thereby 
lowers  its  food  value.  But  the  "wretched  sophistry"  which  ob- 
scures the  nature  of  things  on  a  package  of  prepared  food  mis- 
leads more  persons  and  inflicts  more  injury  upon  the  community 
than  the  other,  yet  goes  unrebuked.  The  most  barefaced  asser- 
tions are  printed  in  magazines,  and  "pure-food  shows"  only  whet 
the  appetite  for  something  new. 

Legal  Definition  of  Adulteration  and  Misbranding. — In  the 
Federal  Pure  Food  Law,  commonly  known  as  the  Food  and  Drugs 
Act  of  June  30,  1906,  adulteration  and  misbranding  are  thus 
defined : 

Sec.  7.  That  for  the  purposes  of  this  Act  an  article  shall  be 
deemed  to  be  adulterated : 


158  AIR,    WATER,    AND    FOOD. 

In  the  case  of  food : 

First.  If  any  substance  has  been  mixed  and  pacjced  with  it  so 
as  to  reduce  or  lower  or  injuriously  affect  its  quality  or  strength. 

Second.  If  any  substance  has  been  substituted  wholly  or  in 
part  for  the  article. 

Third.  If  any  valuable  constituent  of  the  article  has  been 
wholly  or  in  part  abstracted. 

Fourth.  If  it  be  mixed,  colored,  powdered,  coated,  or  stained 
in  a  manner  whereby  damage  or  inferiority  is  concealed. 

Fifth.  If  it  contains  any  added  poisonous  or  other  added  dele- 
terious ingredient  which  may  render  such  article  injurious  to 
health:  Provided,  That  wlien  in  the  preparation  of  food  products 
for  shipment  they  are  preserved  by  any  external  application  applied 
in  such  manner  that  the  preservative  is  necessarily  removed  me- 
chanically, or  by  maceration  in  water,  or  otherwise,  and  directions 
for  the  removal  of  said  preservative  shall  be  printed  on  the  covering 
or  the  package,  the  provisions  of  this  Act  shall  be  construed  as 
applying  only  when  said  products  are  ready  for  consumption. 

Sixth.  If  it  consists  in  whole  or  in  part  of  a  filthy,  decomposed, 
or  putrid  animal  or  vegetable  substance,  or  any  portion  of  an  animal 
unfit  for  food,  whether  manufactured  or  not,  or  if  it  is  the  product 
of  a  deceased  animal,  or  one  that  has  died  otherwise  than  by 
slaughter. 

Sec.  8.  That  the  term  "  misbranded,"  as  used  herein,  shall 
apply  to  all  drugs,  or  articles  of  food,  or  articles  which  enter  into 
the  composition  of  food,  the  package  or  label  of  which  shall  bear 
any  statement,  design,  or  device  regarding  such  article,  or  the 
ingredients  or  substances  contained  therein  which  shall  be  false  or 
misleading  in  any  particular,  and  to  any  food  or  drug  product 
which  is  falsely  branded  as  to  the  State,  Territory,  or  country  in 
which  it  is  manufactured  or  produced. 

That  for  the  purposes  of  this  Act  an  article  shall  also  be  deemed 
to  be  misbranded : 


THE   PROBLEM    OF   SAFE    FOOD.  1 59 

In  the  case  of  food: 

First.  If  it  be  an  imitation  of  or  offered  for  sale  under  the  dis- 
tinctive name  of  another  article. 

Second.  If  it  be  labeled  or  branded  so  as  to  deceive  or  mislead 
the  purchaser,  or  purport  to  be  a  foreign  product  when  not  so, 
or  if  the  contents  of  the  package  as  originally  put  up  shall  have 
been  removed,  in  whole  or  in  part,  and  other  contents  shall  have 
been  placed  in  such  package,  or  if  it  fail  to  bear  a  statement  on 
the  label  of  the  quantity  or  proportion  of  any  morphine,  opium, 
cocaine,  heroin,  alpha  or  beta  eucaine,  chloroform,  cannabis  indica, 
chloral  hydrate,  or  acetanilide,  or  any  derivative  or  preparation  of 
any  of  such  substances  contained  therein. 

Third.  If  in  package  form,  and  the  contents  are  stated  in  terms 
of  weight  or  measure,  they  are  not  plainly  and  correctly  stated  on 
the  outside  of  the  package. 

Fourth.  If  the  package  containing  it  or  its  label  shall  bear  any 
statement,  design,  or  device  regarding  the  ingredients  or  the  sub- 
stances contained  therein,  which  statement,  design,  or  device  shall 
be  false  or  misleading  in  any  particular:  Provided,  That  an  article 
of  food  which  does  not  contain  any  added  poisonous  or  deleterious 
ingredients  shall  not  be  deemed  to  be  adulterated  or  misbranded 
in  the  following  cases : 

First.  In  the  case  of  mixtures  or  compounds  which  may  be 
now  or  from  time  to  time  hereafter  known  as  articles  of  food, 
under  their  ow^n  distinctive  names,  and  not  an  imitation  of  or 
offered  for  sale  under  the  distinctive  name  of  another  article,  if 
the  name  be  accompanied  on  the  same  label  or  brand  with  a  state- 
ment of  the  place  where  said  article  has  been  manufactured  or 
produced. 

Second.  In  the  case  of  articles  labeled,  branded,  or  tagged 
so  as  to  plainly  indicate  that  they  are  compounds,  imitations,  or 
blends,  and  the  word  "compound,"  ''imitation,"  or  ''blend,"  as 
the  case  may  be,  is  plainly  stated  on  the  package  in  which  it  is 


l6o  AIR,   WATER,    AND    FOOD. 

offered  for  sale:  Provided,  That  the  term  blend  as  used  herein 
shall  be  construed  to  mean  a  mixture  of  like  substances,  not  ex- 
cluding harmless  coloring  or  flavoring  ingredients  used  for  the 
purpose  of  coloring  and  flavoring  only:  And  provided  further ,  That 
nothing  in  this  act  shall  be  construed  as  requiring  or  compelling 
proprietors  or  manufacturers  of  proprietary  foods  which  contain 
no  unwholesome  added  ingredient  to  disclose  their  trade  formulas, 
except  in  so  far  as  the  provisions  of  this  act  may  require  to  secure 
freedom  from  adulteration  or  misbranding. 

Extent  of  Adulteration. — In  any  discussion  of  the  extent  to 
which  adulterated  foods  are  sold  it  must  be  borne  in  mind  that 
the  adulterated  articles  make  up  only  a  relatively  small  proportion 
of  the  food  that  actually  passes  over  the  counter.  Flour,  for  ex- 
ample, is  seldom  adulterated ;  pepper,  mustard  and  vanilla  extract 
often  are.  For  one  pound  of  these  substances  sold,  looo  pounds 
or  more  of  flour  go  out  from  the  store.  Figures  given  in  official 
reports  of  food  inspection  do  not  represent  the  case  exactly,  be- 
cause the  inspectors  are  trained  men,  and  purchase  samples  of 
those  lines  of  goods  which  experience  has  shown  them  to  be  most 
likely  to  be  adulterated.  Brands  of  foods  which  they  have  reason 
to  believe  are  pure  they  do  not  sample.  Estimated  on  the  total 
quantity  sold,  it  is  doubtful  if  more  than  5  to  lo  per  cent,  of  the 
food  sold  is  adulterated  in  any  way,  and  these  figures  would  un- 
doubtedly be  much  too  high  for  those  states  in  which  there  is  a 
well-enforced  system  of  food  inspection. 

Character  of  Adulteration. — Much  of  the  present  propaganda 
in  the  interests  of  pure  food  and  the  movement  for  the  protection 
of  the  consumer  can  be  summed  up  in  three  words:  "An  Honest 
Label."  In  many  cases  an  accurate  and  true  statement  of  the 
contents  of  the  can  or  package  is  the  only  protection  needed  by 
the  consumer,  and  is  fully  as  efficient  as  well  as  much  cheaper 
than  prosecutions  or  restrictive  measures.  Many  of  the  terms 
used   on   food    packages   deceive   only   the    ignorant    purchaser. 


THE  PROBLEM  OF  SAFE  FOOD.  l6l 

"Strictly  pure"  is  a  well-understood  trade  term,  with  a  meaning 
known  to  the  initiated;  the  words  "Home-Made"  may  cover 
some  of  the  most  highly  developed  products  of  synthetic  organic 
chemistry. 

The  cases  in  which  the  adulteration  is  of  a  character  dele- 
terious to  health  are  fortunately  few.  The  use  of  canned  goods 
brings  certain  dangers  in  the  dissolved  metals  from  the  cans  or 
from  the  solder,  also  from  a  careless  habit  of  allowing  food  to 
stand  in  the  opened  tins.  The  liking  for  bright  green  pickles  and 
peas  leads  to  coloration  by  copper  salts. 

So  rapidly  do  new  substances  come  upon  the  market  that  it  is 
of  little  use  to  put  into  a  general  text-book  definite  statements  of 
the  quality  of  many  foods.  A  baking-powder  or  a  spice  which  is 
honestly  made  to-day  may  next  week  pass  into  the  hands  of  un- 
scrupulous dealers  who  please  the  pubhc  and  thereby  salve  their 
consciences. 

To  furnish  what  the  people  think  they  want  has  been  the  rule 
from  the  days  of  an  earlier  generation  of  grocers,  who  divided  a 
barrel  of  cooking-soda  in  halves  and  set  one-half  on  one  side  of 
the  store  for  "saleratus"  and  the  other  on  the  opposite  side  for 
soda,  so  that  there  should  be  no  suspicion  in  the  mind  of  the  cus- 
tomer that  the  packages  came  from  the  same  barrel,  and  yet  each 
might  satisfy  his  individual  preference. 

Names  that  have  passed  down  from  a  former  generation  as 
being  above  reproach  are  now  found  to  cover  adulterated  goods. 
The  trademark  has  passed  into  other  and  less  scrupulous  hands, 
and  the  new  owners  do  not  hesitate  to  trade  upon  the  reputation 
earned  by  their  predecessors.  There  are,  however,  several  phases 
of  the  subject  that  should  be  briefly  mentioned. 

Breakfast  Foods, — The  craving  for  something  new  to  stimulate 
a  jaded  appetite  already  spoiled  by  endless  variety  and  bad  com- 
binations has  led  to  the  manufacture  of  a  cereal  preparation  for 
nearly  every  day  in  the  year,  regarding  some  of  which  the  state- 


1 62  AIR,  WATER,    AND    FOOD. 

ment  is  made  that  they  are  ''predigested."  No  better  comment- 
ary on  the  laziness  or  wilful  ignorance  of  American  providers  could 
be  made  than  this.  Little  do  the  people  know  about  wheat  or 
cooking  if  they  suppose  that  grain  can  be  changed  by  manipula- 
tion in  any  kind  of  machine  so  as  to  give  greater  food  value  than 
was  contained  in  the  grain.  While  it  is  true  that  some  of  these 
preparations  are  far  better  than  the  half-cooked  grains  found  on 
so  many  tables,  the  fact  remains  that  it  is  the  cook  and  not  the 
substance  which  is  poor.  The  false  statements  on  food  packages 
of  all  kinds  are  so  absurd  that  they  would  defeat  their  own  pur- 
pose were  they  viewed  in  the  light  of  common  sense.  It  is  not 
always  best  to  have  food  which  is  too  easily  digested. 

A  predigested  food  is  quickly  absorbed  into  the  circulation, 
and  hence  a  small  quantity  causes  a  sensation  of  fulness  and  satis- 
faction, which,  however,  soon  passes  away  and  a  faintness  results. 
This  is  especially  true  of  the  sugars  and  dextrins.  Frequent  meals 
should  go  with  easily  absorbed  foods.  The  rapid  digestion  is  the 
cause  of  much  pernicious  eating  of  sweets  between  meals,  which 
satisfies  the  appetite  for  the  time  being  and  prevents  substantial 
quantities  of  other  foods  being  taken  at  the  time  they  are  offered. 

From  a  study  of  analyses  of  a  large  number  of  foods  the  fol- 
lowing conclusions  are  drawn  by  F.  W.  Robison :  * 

1.  The  breakfast  foods  are  legitimate  and  valuable  foods. 

2.  Predigestion  has  been  carried  on  in  the  majority  of  them 
to  a  limited  degree  only. 

3.  The  price  for  which  they  are  sold  is  as  a  rule  excessive  and 
not  in  keeping  with  their  nutritive  values. 

4.  They  contain  as  a  rule,  considerable  fibre  which,  while  prob- 
ably rendering  them  less  digestible,  at  the  same  time,  may  render 
them  more  wholesome  to  the  average  person, 

5.  The  claims  made  for  many  of  them  are  not  warranted  by 
the  facts. 

*  Mich.  Agr.  Expt.  Sta.,  Bull.  211     {1904). 


THE  PROBLEM  OF  SAFE  FOOD.  1 63 

6.  The  claim  that  they  are  far  more  nutritious  than  the  wheat 
and  grains  from  which  they  are  made  is  not  substantiated. 

7.  They  are  palatable  as  a  rule  and  pleasing  to  the  eye. 

8.  The  digestibility  of  these  products  as  compared  with  highly 
milled  goods,  while  probably  favorable  to  the  latter,  does  not  give 
due  credit  to  the  former,  because  of  the  healthful  influence  of  the 
fibre  and  mineral  matter  in  the  breakfast  foods. 

9.  Rolled  oats  or  oatmeal  as  a  source  of  protein  and  of  fuel  is 
ahead  of  the  wheat  preparations,  excepting  of  course  the  special 
gluten  foods,  which  are  manifestly  in  a  different  class. 

In  general,  the  cost  of  these  foods  is  low  if  they  are  considered 
merely  as  confections  to  please  the  taste,  but  they  are  expensive 
foods  regarded  as  substitutes  for  the  ordinary  cereal  products. 

This  is  well  shown  in  the  following  table  in  which  the  fuel 
value  of  breakfast  foods  and  other  common  food  products  is 
graphically  compared. 

Colors  and  Preservatives  in  Food. — For  many  years  such  sub- 
stances as  alcohol,  vinegar,  sugar,  salt,  and  the  like,  have  been 
used  to  preserve  food.  Such  materials  are  commonly  held  to  be 
harmless  to  persons  of  sound  digestion  if  used  in  moderate  amounts. 
Within  recent  years,  however,  there  has  been  a  constantly  increas- 
ing tendency  toward  the  use  in  food  products  of  such  powerful 
antiseptics  as  formaldehyde,  salicylic  and  benzoic  acids  and  their 
salts,  and  boric  acid.  An  important  distinction  to  be  borne  in 
mind  between  this  class  of  preservatives  and  those  first  named  is 
that  the  former  when  used  in  food  in  quantity  sufficient  to  pre- 
serve it  make  their  presence  known  to  the  consumer  by  either 
their  taste  or  odor.  With  the  chemical  preservatives,  however, 
an  intimation  of  their  presence  is  conveyed  to  the  consumer  only 
by  a  statement  on  the  label.  It  is  the  general  feeling  among  those 
engaged  in  the  enforcement  of  the  food  laws  that  the  common 
use  of  these  preservatives  should  be  forbidden,  or  that  they  should 
l)e  allowed  only  under  certain  definite  restrictions.     The  question 


164 


AIR,    WATER,    AND    FOOD. 


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THE  PROBLEM  OF  SAFE  FOOD.  165 

IS  not  one  of  their  possible  harmful  effect  only,  although  it  cannot 
be  successfully  denied  that  their  unrestricted  use  would  lead  to 
grave  danger  to  health,  especially  in  the  case  of  invalids  and  chil- 
dren, or  those  with  various  degrees  of  digestive  efficiency.  It 
seems  reasonable  to  infer  that  the  processes  of  digestion  being 
largely  the  result  of  bacterial  and  enzymic  action,  will  be  retarded 
or  interfered  with  to  a  greater  or  less  extent  by  substances  which 
inhibit  bacterial  action  in  food. 

There  is,  however,  another  reason  for  objecting  to  the  use  of 
chemical  preservatives.  By  their  use  much  food  that  is  unwhole- 
some and  unfit  for  consumption  can  be,  and  is  placed  upon  the 
market  with  no  warning  to  the  consumer.  "The  man  who  adds 
formaldehyde  to  his  milk  takes  down  the  danger  signal,  but  does 
not  remove  the  danger." 

Similarly,  objections  can  be  made  to  the  use  of  coal-tar  colors 
in  foods.  There  are  hundreds  of  food  packages  which  would 
never  leave  the  grocers'  shelves  were  it  not  for  the  fact  that  by 
the  use. of  artificial  color  their  true  composition  and  the  actual 
nature  of  the  materials  from  which  they  are  made  is  hidden. 
Apart  from  any  question  as  to  the  harmfulness  of  these  dyes, 
there  is  ample  reason  for  their  use  being  strictly  regulated  by 
official  action,  in  that  their  use  except  under  such  supervision 
allows  the  manufacturer  to  sell  inferior  articles  under  the  appear- 
ance of  standard  foods;  it  permits  the  customer  to  be  misled  as 
to  the  strength  and  purity  of  the  product  that  he  buys;  the  age  and 
past  history  of  the  product  may  be  made  a  sealed  book;  finally, 
by  the  use  of  coloring,  an  unwholesome  and  improper  food  may 
be  put  upon  the  market. 

Summary. — The  chief  dangers  in  food  are  from  wrong  pro- 
portions of  proteid,  fat,  and  carbohydrates,  from  fermentable  and 
irritating  decompositions,  from  bad  methods  of  cooking  and  un- 
suitable combinations,  from  transmission  of  micro-organisms  either 
by  exposure  to  dust  or  by  contact  with  filthy  hands  or  vessels,  to  a 


1 66  AIR, 

favorable  medium  for  the  growth  of  pathogenic  germs,  from  un- 
suitable food  scientifically  disguised. 

From  this  hasty  survey  it  will  be  seen  how  little  danger  to 
health  is  incurred  if  only  reasonable  care  is  taken  and  if  the  always 
doubtful  articles  are  avoided. 

Take,  for  instance,  that  most  commonly  adulterated  class, 
spices.  Who  will  say  that  it  may  not  be  better  to  eat  corn  and 
buckwheat  and  ground  peas  than  pure  pepper?  Rice  is  certainly 
a  more  wholesome  food  than  ginger,  and  starch  than  soda.  Glu- 
cose is  even  more  easily  absorbed  than  cane-sugar.  These  are 
cases  of  frauds  on  the  pockets,  but  possibly  blessings  in  disguise 
for  the  stomachs.  When  any  community  is  so  ignorant  as  to  per- 
mit of  such  glaring  cases  of  adulteration  as  coal-tar  dyes  in  food, 
and  gypsum  in  cream  of  tartar,  they  deserve  to  suffer.  It  is 
knowledge  on  the  part  of  each  intelligent  citizen,  w^hich  will  mend 
matters,  even  it  it  is  only  that  kind  of  empirical  knowledge  that 
one  is  forced  to  learn  in  relation  to  electricity  and  steam  in  order 
to  live  in  a  modern  house. 

This  knowledge  is  now  easily  obtained  through  the  city,  state 
and  governmental  laboratories,  and  their  publications  are  acces- 
sible to  all  who  can  read  and  wTite.  There  is  therefore  no  excuse 
for  general  ignorance  and  credulity  as  to  trade  preparations  of 
foods,  any  more  than  for  the  degrading  habit  of  purchasing  patent 
medicines  to  remedy  the  ills  caused  by  the  misuse  of  food.  Both 
together  form  the  saddest  commentary  on  human  weakness  and 
lack  of  rational  thought. 


CHAPTER    X. 


ANALYTICAL    METHODS. 


In  the  discussion  of  the  methods  employed  for  the  ex- 
amination of  food-materials,  only  a  few  typical  substances 
have  been  considered,  and  the  processes  given  are  such  as  to 
bring  into  prominence  the  scientific  aspect  rather  than  the 
technical  detail  of  the  subject;  at  the  same  time  it  is  hoped 
that  a  sufficient  variety  of  methods  is  given  to  enable 
the  student  to  gain  considerable  experience  in  the  necessarily 
short  time  which  can  be  allotted  to  the  subject. 

Both  on  account  of  its  importance  as  a  food-material  and 
on  account  of  its  availability  for  the  various  tests,  milk  has 
been  chosen  as  a  type  of  animal  food;  moreover,  it  may  be 
made  to  serve  as  an  excellent  example  of  the  changes  to 
which  food-materials  are  liable  through  the  growth  of  the 
micro-organisms.  The  analysis  of  milk  includes  determina- 
tions of  specific  gravity,  water,  or  total  solids,  ash,  fat,  nitro- 
gen, and  sugar,  the  separation  of  casein  and  albumin,  and  the 
detection  of  preservatives  and  coiormg  matters. 

The  breakfast  cereals  are  taken  as  typical  of  vegetable 
foods.  The  examination  which  may  be  made  of  this  class 
includes  the  determination  of  moisture,  ash,  fat,  nitrogen  and 
proteids,  starch,  cellulose,  and  the  products  of  peptonization 
and  saccharification. 

The  nature  and  composition  of  the  various  fats  and  oils 

is  briefly  illustrated  by  the   examination  of  butter  and  the 

determination  of  the  principal  constants  of  the  butter-fat. 

167 


1 68  AIR,    WATER,    AND    FOOD. 

The  results  of  fermentation  are  illustrated  by  the  deter- 
mination of  alcohol  in  beer,  wine,  meat  extracts,  patent  medi- 
cines and  "  temperance  drinks,"  flavoring  essences  and  the 
like.  The  determination  of  the  relative  proportion  of  volatile 
and  fixed  acids,  of  the  saccharine  products  of  malting,  and 
of  volatile  oils  or  flavoring  principles,  is  also  instructive. 

A  more  elaborate  discussion  of  the  methods  used  in  food 
analysis  and  of  the  interpretation  of  results  will  be  found  in 
the  larger  works  upon  the  subject.  x\s  reference  books  for  the 
use  of  the  student  in  the  laboratory,  the  following  in  the 
author's  experience,  have  been  found  especially  helpful:  Leach: 
Pood  Inspection  and  Analysis;  Gill:  Handbook  of  Oil  Analysis; 
Sherman:  Organic  Analysis;  Rolfe:  The  Polariscope  in  the 
Laboratory. 

MILK. 

General  Statements. — Milk  is  an  emulsion  of  fat-globules 
with  casein  and  other  nitrogenous  bodies,  mineral  salts 
(probably  in  combination),  sugar  and  water.  The  average 
percentage  composition  of  the  more  important  varieties  of 
milk,  as  found  by  recent  observers,  is  summ.arized  in  the  fol- 
lowing table: 

Water.  Sug^ar.  Proteids.  Fat.  Ash. 

Cow 86. go  4.80  3.60  4.00  0.70 

Human 88.75  6.00  1.50  3.45  0.30 

Goat 85.70  4.45  4.30  4.75  0.80 

Ass 89.50  6.25  2.00  1.75  0.50 

Mare 90.75  5-7o  2.00  1.20  0.35 

Sheep 80.80  4.90  6.55  6.85  0.90 

In  connection  with  this  table  should  be  noticed  the  high 
proportion  of  sugar  and  low  proportion  of  casein  and  ash  in 
human  milk  as  compared  with  cow's  milk.  The  former  is  not 
readily  curdled,  the  casein  never  separating  in  a  compact  clot 
which  settles  to  the  bottom,  a  difference  which  is  attributed 
to  the  lower  proportion  of  fat  to  casein.* 

The  average  composition  of  14,967  samples  of  cow's  milk 

*  Lehmann  and  Hempel:   Arch.  Physiol.,  56  (18^4),  558. 


food:  analytical  methods:  milk. 


169 


for  the  year  1907,  analyzed  directly  on  arrived  of  the  milk  from 
the  farm,  is  given  by  Richmond*  as  follows: 

Average,  1907. 

Specific  gravity i .0322 

Total  solids 1 2 .  69 

Solids  not  fat 8 .  94 

^^^ 3-75 

The  U.  S.  standard  for  whole  milk  requires  that  it  shall 
contain  not  less  than  8.5  per  cent  of  solids  not  fat,  and  not 
less  than  3.25  per  cent  of  milk  fat.f 

From  the  average  values  there  are  constant  variations,  due 
to  the  time  of  milking,  the  season  of  the  year  and  the  breed  and 
feed  of  the  cow.  The  proportion  of  milk  sugar  and  ash  is  most 
nearly  constant,  while  the  fat  is  the  most  variable  constituent. 

An  examination  of  milk  as  regards  its  healthfidness  usually 
consists  in  determining  what  changes,  if  any,  have  taken  place 
in  its  constituents  due  to  the  growth  of  micro-organisms. 
Milk  is  a  natural  culture  medium  for  the  growth  of  micro- 
organisms and  they  increa.'e  in  it  with  almost  incredible 
rapidity.  These  changes  which  take  place  are  called  "  fer- 
mentations." The  two  most  common  are  the  acid  and  the 
alkaline. 

Acid  Fermentation. — Milk-sugar  is  converted  wholly  or  in 
part  into  lactic  acid  under  the  influence  of  a  class  of  organisms 
of  which  bacillus  acidi  lactici  is  the  best  known  and  is  generally 
regarded  as  predominating.  The  extent  to  which  this  change 
has  taken  place  is  shown  by  the  test  for  acidity. 

Alkaline  Fermentation. — In  the  alkaline  fermentation  the 
albumin  and  casein  are  decomposed  with  the  formation  of 
ammonia  and  other  intermediate  nitrogenous  products,  some 
of  them  of  a  poisonous  character,  as  is  shown  by  the  preval- 
ence of  cholera  infantum  when  such  decomposed  milk  is  used, 

*  Analyst^  igo8. 

t  Circular  No.  19,  Office  of  the  Secretary,  U.  S.  Dept.  Agriculture. 


lyo  AIR,  WATER,    AND   FOOD. 

and  by  cases  of  poisoning  by  ice-cream,  etc.  This  fermenta- 
tion generally  occurs  simultaneously  with  the  acid  fermen- 
tation, but  at  first  is  much  less  active;  at  a  subsequent  stage, 
however,  the  alkaline  fermentation  becomes  more  pro- 
nounced, and  in  certain  cases  may  completely  dominate  the 
other  fermentations. 

Other  Fermentations. — Butyric  acid  fermentation  may  be 
a  result  of  the  action  of  one  or  several  groups  of  bacteria  upon 
the  glyceride  of  butyric  acid.  This  action  sets  free  the  butyric 
acid  in  part  and  the  fat  becomes  in  time  "  rancid,"  but  this 
change  takes  place,  as  a  rule,  more  slowly  and  is  not  so  com- 
mon as  the  others. 

The  production  of  koumiss  is  an  instance  of  an  artificially 
incited  change.  Various  other  fermentations  occasionally 
occur  which  cause  a  slimy  appearance  or  a  bitter  taste. 
Various  colors  may  be  imparted  to  the  milk  by  the  presence 
of  chromo genie  or  color-producing  micro-organisms.  The 
student  is  referred  to  the  various  journals  and  to  text-books 
on  dairy  bacteriology  for  accounts  of  these  less  important 
changes. 

Sampling. — In  all  manipulations  with  milk  the  importance 
of  thorough  and  frequent  mixing,  not  shaking,  cannot  be  too 
strongly  emphasized;  this  is  best  accomplished  by  pouring  it 
from  one  vessel  to  another.  This  will  be  found  necessary 
even  when  the  milk  has  been  standing  for  only  a  few  minutes, 
on  account  of  the  rapid  rise  of  the  cream.  The  apparatus 
used  to  contain  or  to  measure  milk  should  be  thoroughly 
washed  out  as  soon  as  possible. 

PHYSICAL    TESTS. 

Specific  Gravity. — Take  the  specific  gravity  in  the  usual 
manner  by  means  of  a  hydrometer  at  15°. 6  C.  If  the  temper- 
ature of  the  milk  varies  only  a  few  degrees  from  this,  the  read- 
ing may  be  corrected  by  means  of  Table  IX,  Appendix  A. 


food:  analytical  methods:  milk.  171 

Hydrometers  for  special  use  with  milk  are  known  as  lac- 
tometers and  are  usually  so  graduated  as  to  read  in  degrees 
corresponding  to  the  gravity.  Thus  in  the  Quevenne  lactometer, 
the  graduation  from  15°  to  40°  corresponds  to  a  specific  gravity 
1. 015  to  1.040. 

The  New  York  Board  of  Health  lactometer  has  an  arbitrary 
scale,  reading  zero  in  pure  water  and  100  in  "  pure  milk,"  wiiich 
is  taken  as  corresponding  to  a  specific  gravity  of  1.029.  From. 
the  scale-reading  the  specific  gravity  may  readily  be  calculated. 

Notes. — The  specific  gravity  of  mi'k  is,  in  the  main,  a  func- 
tion of  two  factors,  namely,  the  percentage  of  solids  not  fat 
and  of  the  fat.  The  former  raises  it;  the  latter  lowers  it.  The 
determination  of  the  specific  gravity  alone  is  not  to  be  relied 
upon  as  an  absolute  index  of  the  purity  of  the  milk.  The 
specific  gravity  varies  in  general  from  1.029  to  1.034,  and  in 
most  cases  of  normal  and  w^ell-mixed  milk  from  several  cows 
the  specific  gravity  will  lie  between  1.030  and  1.032. 

Opacity.  —  The  white  color  and  opacity  of  milk  are 
largely  due  to  the  presence  of  the  suspended  fat-globules  and 
of  the  casein  in  colloidal  form.  The  influence  of  the  latter  is 
shown  by  the  fact  that  the  color  of  milk  is  not  greatly 
changed  after  it  has  passed  through  a  centrifugal  separator 
which  removes  practically  all  of  the  fat.  The  degree  of 
opacity  and  the  percentage  of  fat  may  be  determined  by 
means  of  Feser's  lactoscope,  the  modus  operandi  of  which  is 
given  with  that  instrument.  Another  instrument  of  like  prin- 
ciple is  Heeren's  pioscope,*  which  consists  of  an  ebonite  disk 
w^ith  a  raised  rim;  a  drop  or  two  of  milk  is  placed  upon  it,  the 
painted  glass  cover  placed  over  it,  and  the  color  of  the  milk 
matched  with  one  of  those  on  the  cover. 

Cream. — Fill  the  creamometer,  an  elongated  test-tube 
w^th  graduations  near  the  top,  to  the  zero  mark  with  the 

'^Repit.f.  Anal.  Chem.,    1881,  247. 


172  AIR,    WATER,    AND    FOOD. 

milk,  add  three  drops  of  a  solution  of  methyl  violet,  mix  and 
put  away  in  a  cold  place.  After  twenty-four  hours  read  ofif 
the  percentage  of  cream. 

Notes. — The  rapidity  with  wdiich  the  cream  rises  indicates 
whether  sodium  carbonate  has  been  added,  its  action  being 
to  retard  the  rise  of  cream  so  that  the  milk  is  never  blue. 
Should  the  cream  separate  very  quickly  and  the  milk  be  blue, 
the  indication  is  that  water  has  been  added  or  that  the  milk 
is  of  poor  quality.  The  method  is  only  approximate  and  does 
not  give  the  amount  of  fat.  The  methyl  violet  is  added  to 
render  the  reading  sharper,  as  it  does  not  dissolve  appreciably 
in  the  cream.  Cream  contains  most  of  the  fat  of  milk  with  a 
small  proportion  of  the  other  constituents.  loio  samples  of 
cream  gave  an  average  of  48.3  per  cent.  fat. 

CHEMICAL   TESTS. 

Reaction. —  Normal  milk  gives  the  amphoteric  reaction, 
that  is,  it  turns  delicate  litmus  both  red  and  blue.  This  is  due 
to  the  presence  of  neutral  and  acid  phosphates  of  the  alkalies. 
The  reaction  of  the  milk  soon  becomes  acid,  however. 

Acidity.  —  Measure  5  c.c.  of  milk  into  a  small  beaker, 

N 
dilute  with   sO  c.c.   of  water,  and  titrate  the  acid   with  — 

10 

sodium  hydroxide,  using  phenolphthalein  as  an  indicator. 
Express  the  acidity  in  degrees,  considering  each  tenth  of  a 
cubic  centimeter  of  sodium  hydroxide  one  degree. 

Notes. — The  acidity  of  milk  is  due  to  the  fermentation  of 
milk-sugar  and  the  production  of  lactic  acid.  Under  favor- 
able circumstances  this  change  may  take  place  with  consid- 
erable rapidity.  For  example,  six  hours  after  milking  the 
acidity  may  be  fourteen  to  twenty-five  degrees;  forty-eight 
hours  after  milking  it  may  reach  one  hundred  degrees.  When 
the  acidity  reaches  twenty-three  degrees  milk  coagulates  on 


food:  analytical  methods:  milk.  173 

boiling.*     An  example  of   the  rate   of  change  is  given  in  the 
following  table  :t 

Oav  Acidity,  Sugar, 

■'•  c.c.  Degrees  of  Rotation. 

1 2.2  25.2 

2 5-5  23.1 

3   II. o  21.6 

b 13.2  14.2 

7 I5-0  9-4 

8 16.3  7.8 

9 17.2  1.2 

Total  Solids. — The  determination  of  total  solids  is  best 
carried  out  in  a  platinum  dish  having  a  flat  bottom  about  2^ 
inches  in  diameter.  Small  dishes  of  aluminum  or  lead  foil,  or 
blacking-box  covers  answer  very  well,  but  of  course  cannot  be 
ignited  to  obtain  the  ash. 

Directions. — Weigh  the  platinum  dish  and  add  about  5.1 
grams  to  the  weights  on  the  balance-pan.  With  the  burette 
pipette  deliver  5  c.c.  of  the  well-mixed  milk  into  the  dish  and 
weigh  the  whole  as  rapidly  as  possible  to  the  nearest  milli- 
gram. Evaporate  the  milk  to  dryness  on  the  water-bath  and 
then  dry  it  in  the  oven  at  100°  to  constant  weight. 

Notes. — It  is  important  that  the  milk  should  be  in  the  form 
of  a  thin  layer,  so  that  the  evaporation  of  the  water  shall  take 
place  as  quickly  as  possible.  Under  these  conditions  the  resi- 
due obtained  is  nearly  white;  but  if  the  process  be- prolonged, 
it  may  have  a  brownish  color  from  the  caramelization  of  the 
sugar.  4 

Various  analysts  have  proposed  modifications  of  the  pro- 
cedure as  described  above,  such  as  drying  on  sand  or  asbestos,, 
coagulation  of  the  milk  by  absolute  alcohol  before  evaporation,, 
and  so  forth,  but  simple  evaporation  in  an  open  dish  is  generally 
regarded  as  the  most  advantageous. 

Ash. — Directions. — Ignite  the  platinum  dish  containing 
the   residue   from  the  preceding  determination   at   a  low  red 

*  Thorner:    Analyst,  i6  (iSpi),  200. 

t  "  Thesis,"  Ethel  B.  Blackwell,  M.I.T.,  1891. 


174  AIR,    WATER,    AND    FOOD. 

heat  until  the  ash  is  white  or  nearly  so.  This  may  be  done 
over  a  burner  carefully  regulated  so  that  the  dish  is  nowhere 
heated  above  a  dull  redness,  or  in  a  muffle  furnace.  After 
weighing  the  ash,  test  it  for  carbonates  by  adding  two  drops 
of  dilute  hydrochloric  acid.  Efferv^escence  in  the  ash  is  quite 
perceptible  when  carbonates  are  present  in  as  small  amount 
as  0.05  per  cent.  If  desired,  the  hydrochloric  acid  solution  of 
the  ash  can  be  used  to  test  for  boric  acid  as  described  on  page 
188. 

Notes. — If  the  temperature  is  raised  too  much  during  ignition, 
the  results  will  be  low  on  account  of  the  partial  volatilization 
of  the  chlorides  of  the  milk;  hence  the  process  should  be 
carried  out  at  as  low  a  temperature  as  wiU  admit  of  the  oxida- 
tion of  the  carbonaceous  matter. 

The  percentage  composition  of  the  ash  of  milk  is  given 
by  Fleischmann  and  Schrodt  *  as  follows: 

Per  cent. 

Potassium  oxide,  KjO 25.42 

Sodium            "        Na^O IO-94 

Calcium           "        CaO 21.45 

Magnesium    "        MgO 2.54 

Ferric               "        FeaOs c.ii 

Sulphuric  acid,      SO3 4. 11 

Phosphoric"         P2O5 24.11 

Chlorine,                 CI 14.60 

103.28 
Less  oxygen  corresponding   to  chlorine  f       3.28 

100.00 

The  ash  of  genuine  cow's  milk  is  free  from  carbonates  and 
borates,  and  the  ash  soluble  in  water  is  about  30  per  cent,  of 
the  total.  The  ash  determined  in  this  way  does  not  represent 
exactly  the  mineral  salts  present  in  the  milk,  since  these  are 
altered  by  the  oxidation  to  some  extent. 

*  Baumeister:  "  Milch  und  Molkerei-Producte."  S.  16. 

f  This  correction  is  necessary  because  the  metals  are  all  calculated  as 
oxides,  when,  as  a  matter  of  fact,  a  certain  proportion  are  present  as 
chlorides. 


food:  analytical  methods:  milk.  175 

Fat.  —  Since  the  fat  is  so  important  a  constituent  of  milk, 
an  endless  variety  of  methods  and  modifications  for  its  deter- 
mination have  been  devised.  The  processes  which  are  in 
most  general  use  may  be  divided  into  three  classes: 

1.  Estimation  of  the  fat  by  simple  extraction  of  the  milk, 
best  dried  on  some  absorbent  material. 

2.  Volumetric  estimation  of  the  fat  liberated  by  chemical 
treatment  from  the  milk  and  collected  by  centrifugal  force. 

3.  Estimation  of  the  fat  by  extraction  from  the  milk  itself 
after  solution  of  the  casein  by  acid. 

A  typical  method  from  each  class  will  be  described  in  de- 
tail. 

(i)  Adams'  Method.  —  Directions. — Roll  a  strip  of  fat- 
free  blotting-paper,  22  inches  long  and  2^  inches  wide,  into 
a  rather  loose  coil  and  fasten  it  by  a  bit  of  copper  wire.  Hold 
the  coil  in  one  hand  and  carefully  run  on  to  the  upper  end  of 
it  5  c.c.  of  milk  from  a  burette  pipette.  Place  the  coil,  diy 
end  downward,  in  the  water-oven  and  dry  it  for  an  hour. 
When  dry  remo\  e  the  wire  and  place  the  coil  in  the  Soxhlet 
extractor.  If  preferred,  the  strip  of  paper  may  be  held  hori- 
zontally in  a  frame  and  the  milk  run  on  to  it.  When  dry  the 
paper  is  rolled  into  a  coil  and  extracted.  Weigh  the  extraction- 
flask,  place  in  it  75  to  100  c.c.  of  petroleum  ether  and  connect 
the  extractor  with  the  condenser.  After  the  coil  has  been 
extracted  for  at  least  two  hours  remove  the  extractor  and 
evaporate  the  petroleum  ether  at  low  temperature,  taking  care 
to  avoid  the  vicinity  of  free  flames.  Dry  the  flask  with  the 
extracted  fat  in  the  water  oven  to  constant  weight.  Avoid  pro- 
tracted heating,  which  would  cause  partial  oxidation  of  the  fat. 

Notes. — Absorbent  paper  exercises  a  selective  action  on 
the  constituents  of  milk  so  that  the  fat  is  left  on  the  surface  of 
the  paper,  mixed  with  only  about  one-third  of  the  non-fatty 
solids,  and  hence  it  is  more  easily  extracted;  further,  owing 
to  the  greatly  increased  surface  exposed,  the  extraction  of  the 
fat  is  practically  complete. 


176 


AIR,    WATER,    AND    FOOD. 


Ethyl  ether  may  be  used  instead  of  petroleum  ether,  but  care 
should  be  taken  that  the  ether  is  perfectly  dry,  otherwise  other 
substances  than  fat,  principally  milk-sugar,  will  be  extracted. 
On  the  other  hand,  substituted  glycerides  may  not  be  dissolved 
out  by  ether.  For  these  reasons  the  petroleum  ether  is  to  be 
preferred  as  a  solvent,  although  its  action  is  considerably 
slower  than  that  of  the  other. 

Owing  to  the  inflammable  nature  of  the  solvents  employed. 


Fig.  12. — Apparatus  for  Fat  Extraction. 

it  is  best  not  to  use  a  flame  as  the  source  of  heat,  but  to  heat 
the  flask  by  means  of  a  steam-  or  water-bath.  In  this  labora- 
tory small  electric  heaters  about  4  inches  in  diameter  are  used 
and  have  been  found  safe  and  convenient.  The  complete 
apparatus  is  shown  in  Fig.  12.  In  using  these  it  should  be 
borne  in  mind  that  considerable  quantities  of  ether  or  petroleum 
ether  in  contact  with  the  heatea  surface  may  ignite,  and  caution 
should  be  taken  not  to  evaporate  any  quantity  of  these  solvents 
from  an  open  vessel. 

(2)  Babcock  Method. — Directions. — Measure  17.6   c.c.   of 
the  milk  from  a  pipette  into  the  long-necked,  graduated  whirling- 


food:  analytical  methods.  177 

bottle.  Measure  out  17.5  ex.  of  sulphuric  acid  i^d.  gr.  1.83), 
and  add  it  gradually  to  the  milk,  mixing  the  t^^->  thoroughly 
after  each  addition.  Take  care  that  none  of  the  liquid  spurts 
into  the  neck  of  the  bottle.  After  mixing  the  nulk  and  acid, 
and  while  the  bottles  are  still  hot,  place  them  in  opposite 
pockets  in  the  centrifugal  machine,  in  even  numbers,  and 
whirl  them  for  five  minutes,  at  full  speed.  Then  remove  the 
bottles  and  add  hot  water  up  to  the  necks,  after  which  whirl 
them  again  for  one  minute.  Again  add  hot  water  until  the 
fat  rises  to  the  8  mark  on  the  stem.  Place  the  bottles  in  the 
machine  and  whirl  them  at  the  same  rate  as  before  for  one 
minute.  Then  measure  the  length  of  the  column  of  fat  by  a 
pair  of  dividers,  the  points  being  placed  at  the  extreme  limits 
of  the  column,  the  fat  being  kept  warm,  if  necessary,  by  standing 
the  bottle  in  hot  water..  If  now  one  point  of  the  dividers  is 
placed  at  the  zero  mark  of  the  scale  on  the  bottle  used,  the  other 
will  indicate  the  per  cent,  of  fat  in  the  milk. 

Notes. — When  the  acid  and  milk  are  mixed  the  mixture 
becomes  hot  from  the  action  of  the  acid  on  the  water  in  the 
milk  and  turns  dark-colored  on  account  of  the  charring  of 
the  milk-sugar.  The  casein  is  first  precipitated  and  then 
dissolved.  The  fat  is  thus  separated  in  a  pure  state  from  the 
other  constituents  of  the  milk. 

The  fat  obtained  should  be  of  a  clear,  golden-yellow  color, 
and  distinctly  separated  from  the  acid  solution  beneath  it. 
If  the  fat  is  light-colored  or  whitish,  it  generally  indicates  that 
the  acid  is  too  weak,  and  a  dark-colored  fat  with  a  stratum 
of  black  particles  below  it  indicates  that  the  acid  is  too  strong. 
The  best  results  will  be  obtained  by  the  use  of  acid  of  the 
strength  noted  above. 

A  violet  color  is  sometimes  produced  when  the  first  por- 
tions of  the  acid  and  milk  are  mixed.  This  frequently  indi- 
cates the  presence  of  formaldehyde.     (See  p.  187.) 


178 


AIR,    WATER,    AND    FOOD. 


(3)  Gottlieb  Method. — Directions. — Measure  5  c.c.  of  milk 
into  a  glass-stoppered  50-cx.  cylinder  and  add  the  following 
reagents,  being  careful  to  add  them  in  the  order  given  and  to 
shake  the  stoppered  cylinder  thoroughly  after  the  addition  of 
each  reagent:  i  c.c.  of  ammonia,  sp.  gr.  0.96,  5  c.c.  of  alcohol, 
12.5  c.c.  of  ethyl  ether  and  12.5  c.c.  of  petroleum  ether.  Let 
the  cylinder  stand  until  the  lower  layer  is  free  from  bubbles, 
over  night  if  necessary. 

With  ordinary  milk  the  separation  takes  place  rapidly,  but 
with  sweetened  condensed  milk  the  longer  time  may  be  necessary. 
Transfer  the  upper  layer  to  a  tared  flask  by  means  of  the 
apparatus  shown  in  Fig.  13.  This  consists  of  a  cork  carrying 
an  ordinary  glass  T  tube.  Through  the  straight 
limb  of  the  T  tube  slides  a  bent  glass  tube, 
which  is  turned  up  at  the  lower  end.  The  tube 
is  adjusted  by  sliding  it  through  the  rubber 
collar  (C)  so  that  the  lower  end  rests  just  above 
the  junction  of  the  two  layers.  On  then  blow- 
ing gently  in  the  side  arm  (5),  the  upper  layer 
is  forced  out  into  the  flask.  Repeat  the  extrac- 
tion once,  using  10  c.c.  each  of  ether  and  pe- 
troleum ether  and  blowing  it  off  into  the  flask. 
Distil  off  the  solvent  and  dry  the  residual  fat 
to  constant  weight  in  the  water  oven. 

Notes. — It  is  almost  useless  to  try  to  extract 
the  fat  from  milk  by  shaking  it  directly  with 
a  solvent.  An  emulsion  is  formed  with  the  other  constituents 
of  the  milk,  and  it  is  impossible  to  get  a  good  separation  of 
the  solvent  even  with  the  centrifugal  machine.  This  is  prob- 
ably due  to  the  action  of  the  colloidal  casein,  because  it  is 
found  that  when  a  complete  or  partial  solution  of  the  casein 
is  effected  it  is  comparatively  easy  to  extract  and  separate 
the  fat  by  a  solvent  immiscible  with  water. 


food:  analytical  methods:  milk.  179 

The  method  is  apphcable  to  whole  milk  but  is  especially 
valuable  in  determining  fat  in  such  products  as  skim  milk  or 
butter  milk,  which  are  low  in  fat.  It  is  also  of  value  in  the 
analysis  of  sweetened  condensed  milk. 

Relation  between  Specific  Gravity,  Fat,  and  Solids 
in  Milk. — As  has  been  stated  already,  the  specific  gravity 
of  milk  is,  in  the  main,  a  function  of  two  factors,  namely, 
the  percentage  of  solids  not  fat  and  that  of  the  fat.  The  former 
raises  it,  the  latter  lowers  it.  Taken  by  itself  it  affords  very 
little  indication  of  the  composition,  but  if  any  other  item  be 
known,  it  should  be  possible  to  find,  by  calculation,  the  other 
quantities,  provided  the  assumption  is  true.  The  solids  not 
fat  are  made  up  of  several  fluctuating  constituents,  but  ''  nor- 
mal milk  "  seems  to  contain  them  in  such  a  constant  ratio 
that  a  calculation  serves  at  least  to  detect  an  abnormal  sam- 
ple. For  example,  given  the  specific  gravity  and  solids  to 
calculate  the  fat: 

Specific  gravity  =  Gr.  The  amount  which  each  per  cent, 
of  solids  not  fat  raises  the  specific  gravity  =  s.  The  amount 
which  each  per  cent,  of  fat  lowers  the  specific  gravity  =  f. 
Total  solids  =  T.  Solids  not  fat  =  5".  Fat  =  F.  Gr  ^^  Ss 
—  Ff\  or,  substituting  for  vS  its  value  T  —  F;  Gr  =^  (T  —  F) 
5  —  Ff.  The  uncertainty  of  the  calculation  lies  in  the  val- 
ues of  ^  and  f,  which  have  not  been  quite  satisfactorily  deter- 
mined. 

At  different  times  various  formulae  have  been  proposed 
for  this  calculation,  varying,  as  a  matter  of  course,  with 
tha  method  of  fat  extraction  employed.  The  one  most 
extensively  used  is  that  of  Hehner  and  Richmond,*  which 
is    based   on    extensive    observation     and    perfected    process 

*  Analyst,  13  {1888),  26;   17  {1892),  170. 


l8o  AIR,  WATER,    AND    FOOD. 

of    fat  extraction.     This   formula    is    generally  stated  as  fol- 
lows: 

F  =  0.8597  —  0.2186G, 

where /'represents  the  fat,  7"the  total  solids,    and   G    1000   X 
(specific  gravity  —  i.ooo). 

The    simple    formula    -F  =   T  —   —  answers  within    the 

limits   of   experimental    error   for   normal   milk,    but    not    for 
skimmed  or  watered  milk. 

Example. — Data:  Gr  =z  1.0323;  G  ^=  {Gr  —  i)  X  1000  = 
32.3;    T=  12.90. 

5  32.3 

—F=\2.go '—.     i^~  4.02  calculated,      3.99  found. 

5  4 

A  similar  relation  has  been  worked  out  for  the  p'Oteids 
and  sugar,  so  that  from  three  determinations  the  whole  com- 
position may  be  calculated.     Example  as  above: 

Ash     —  .yo  =  A. 

Formula:   P=  2.87+  2.5^  —  3.33/^-  .68-^, 

Gr. 

or  P=  36. 12  +  1.75  —  13.32  —  21.28  —  3.27. 

Sugar=  r- (^+P+i^) 

=  12.90  -  (.70  +  3.27  +  4.02)  -^  4.91. 

Where  a  number  of  calculations  are  to  be  male,  Rich- 
mond's milk-scale  will  be  found  convenient.  Th's  is  an  in- 
strument based  on  the  principle  of  the  slide-rule,  havmg  three 
scales,  two  of  which,  for  the  fat  and  the  total  solids,  are 
marked  on  the  body  of  the  rule,  while  that  for  the  spe:ifi? 
gravity  is  marked  on  the  sliding  part.  Extended  tables  are 
also  used  for  the  same  purpose. 


*  Analyst,  13  {1888),  26;   17  {18 g2),  170. 


food:   analytical  methods:  milk.  i8i 

Milk-sugar.— The  methods  for  the  determination  of  the' 
sugar  in  milk  may  be  divided  into  two  general  classes:  (i) 
those  depending  on  the  reducing  power  of  the  sugar  upon  an 
alkaline  copper  solution;  (2)  those  which  are  based  upon 
observations  of  the  degree  of  rotation  of  the  plane  of  polarized 
light. 

(i)  Determination    by    Fehling's   Solution    according   to 
Munson  and  Walker.* 

Directions. — The  milk  must  first  be  clarified  to  remove 
substances  other  than  sugar  which  would  exert  a  reducing 
action  on  the  Fehling's  solution. 

Measure  25  c.c.  of  milk  into  a  500-c.c.  calibrated  flask.     Add 

about  400  c.c.  of  water,  10  c.c,  of  Fehling's  copper  sulphate 

N 
solution,  then  35  c.c.  of  —  NaOH,  and  make  up  to  500  c.c. 

Mix  thoroughly  and  filter  through  a  dry  filter. 

Determination. — In  a  No.  3  beaker  mix  25  c.c.  of  the  Fehling's 
copper  sulphate  solution  and  25  c.c.  of  the  alkaline  tartrate 
solution.  Add  50  c.c.  of  the  milk  sugar  solution,  prepared  as 
above,  cover  the  beaker  with  a  watch  glass,  and  heat  it  upon 
wire  gauze.  Regulate  the  flame  so  that  boiling  shall  begin  in 
four  minutes,  and  continue  the  boiling  for  exactly  two  minutes. 

Filter  the  cuprous  oxide  without  delay  through  asbestos  in 
a  weighed  Gooch  crucible,  wash  it  with  hot  water  until  free 
from  alkali,  pour  out  the  hot  filtrate,  then  wash  with  10  c.c. 
of  alcohol  and  finally  with  10  c.c.  of  ether.  Dry  the  crucible 
for  30  minutes  at  the  temperature  of  boiling  water  and  weigh. 
Find  the  milligrams  of  lactose  monohydrate  corresponding  to 
the  weight  of  cuprous  oxide  from  Table  XII  on  page  248  and 
calculate  the  percentage  present  in  the  milk. 

*  J.  Am.  Chem.  Soc.  {1906),  663;  {igoy),  541. 


l82  AIR,    WATER,    AND    FOOD. 

Notes. — The  general  principle  upon  which  all  these  methods 
depend  is  based  on  the  fact  that  certain  sugars,  among  which 
is  lactose,  have  the  power  of  reducing  an  alkaline  solution  of 
copper  to  a  lower  state  of  oxidation  in  which  copper  is  separated 
as  cuprous  oxide.  The  copper  salt  which  is  found  to  give  the 
most  delicate  and  reliable  reaction  is  the  tartrate.  The  two 
solutions  which  make  up  the  Fehling's  solution  are  best  preserved 
separately,  and  ir.ixed  only  when  wanted  for  use,  as  otherwise 
the  reducing  power  of  the  solution  is  liable  to  change. 

The  amount  of  reduction  of  the  copper  salt  to  the  cuprous 
oxide  is  affected  by  the  rate  at  which  the  sugar  solution  is 
added,  the  time  and  degree  of  heating,  and  the  strength  of 
the  sugar  solution;  hence  the  necessity  for  adopting  a  definite 
procedure  and  for  taking  the  results  from  a  table  determined 
by  exactly  the  same  procedure  for  varying  amounts  of  the 
sugar. 

The  asbestos  which  is  used  should  be  previously  boiled  in 
nitric  acid  and  then  in  dilute  sodium  hydroxide  and  thoroughly 
washed.  A  layer  about  a  centimeter  thick  should  be  used  in 
the  crucible,  and  a  "  blank  "  determination  made  with  the 
Fehling's  solution  should  not  show  a  change  in  weight  greater 
than  one-half  milligram.  After  the  precipitated  cuprous  oxid:. 
has  been  weighed  it  may  be  dissolved  in  hot  dilute  nitric  acid, 
the  asbestos  in  the  crucible  washed  and  dried  as  described, 
when  it  is  again  ready  for  use.  Do  not  remove  the  asbestos 
from  the  crucible. 

(2)  Determination  by  the  Saccharimeter.  —  For  the 
optical  determination  of  milk-sugar  the  method  of  double  di- 
lution, as  described  by  Wiley  and  Ewell,*  will  be  found  satis- 
factory. 

Directions. — Into  each  of  two  flasks,  marked  at  100  and 
200  c.c,  respectively,  put  65.52  grams  of  milk,  add  10  c.c.  of 
acid  mercuric  nitrate,  fill  to  the  mark,  and  mix  by  shaking. 

*  Analyst,  21   (i8g6\  182. 


food:  analytical  methods:  milk.  183. 

Filter  through  dry  filters  and  polarize  in  a  400-millimeter 
tube,  using  the  Schmidt  and  Haensch  saccharimeter.  Cal- 
culate the  results  as  in  the  following  example: 

Weight  of  milk  used  =  65.52  grams; 

Reading  from  loo-c.c.  flask  =  20°. 84; 
**  *'      200-C.C.  flask  =  10°.  15. 

Then  10.15  X  2  =  20.30; 

20.84  —  20.30  =  0.54; 
0.54  X  2  =  1.08; 

20.84  —   1.08     =  19.76; 
19.76  -T-  4  =  4.94,  which  is  the  per  cent. 

of  milk-sugar. 

Notes. — The  object  in  using  the  method  of  double  dilu- 
tion is  to  avoid  the  necessity  of  making  corrections  for  the 
volume  of  the  precipitate  of  casein  and  fat.  The  method  is 
based  on  the  fact  that,  within  certain  limits,  the  polarizations 
of  two  solutions  of  the  same  substance  are  inversely  propor- 
tional to  their  volumes. 

The  flasks  should  be  filled  at  nearly  the  same  temperature 
as  that  at  which  the  polarizations  are  made,  and  the  tem- 
perature of  the  room  should  be  kept  as  nearly  as  possible 
at  20°  to  avoid  errors  arising  from  marked  changes  in  tem- 
perature. 

PROTEIDS   OF   MILK. 

Determination  of  Total  Proteids. — Weigh  5  grams  of 
milk  into  a  digestion  flask  and  determine  the  nitrogen  by  the 
Kjeldahl  process,  as  directed  on  page  206.  Multiply  the  per 
cent,  of  nitrogen  by  the  factor  6.38  to  obtain  the  per  cent,  of 
proteids.  The  frothing  of  the  alkaline  solution  during  the 
distillation  may  be  prevented  by  the  addition  of  a  piece  of 
paraffin  about  the  size  of  a  bean. 


184  AIR,    WATER,    AND    FOOD. 

Determination  of  Casein  and  Albumin.* — Directions. — 
To  10  grams  of  milk  add  90  c.c.  of  water  at  40-42°  C.  and 
then  1.5  c.c.  of  10  per  cent,  acetic  acid.  Agitate  and  warm 
at  the  above  temperature  until  a  flocculent  precipitate  sepa- 
rates, leaving  a  clear  supernatant  liquid.  Filter,  wash,  and 
determine  the  nitrogen  in  the  washed  precipitate  and  filter  by 
the  Kjeldahl  process.     Multiply  by  6.38  for  the  casein. 

To  determine  the  albumin  neutralize  the  filtrate  with 
caustic  alkali  and  phenolphthalein  and  heat  it  at  100°  C.  until 
the  precipitate  settles  clear.  Filter,  wash,  and  determine  the 
nitrogen  as  before.     Nitrogen  multiplied  by  6.38  equals  albumin. 

Notes. — The  principal  proteid  bodies  present  in  milk  are 
casein  and  albumin.  Others  are  present  in  much  smaller 
quantity,  such  as  fibrin  or  globulin. 

Different  observers  at  various  timies  have  claimed  the 
presence  of  other  nitrogenous  bodies,  but  these  have  not  been 
entirely  substantiated. 

It  is  now  generally  held  that  the  colloidal  state  in  which  the 
casein  is  held  in  milk  is  due  to  the  combination  with  it  of  certain 
mineral  compounds,  chiefly  those  of  calcium.  The  action  of 
precipitants  is  on  these  mineral  matters,  breaking  up  the  com- 
l)ination  and  releasing  the  insoluble  casein. 

Interpretation  of  Results. — The  most  common  forms  of 
adulteration  of  milk  are  the  addition  of  water  and  the  removal 
•of  cream.  Occasionally  some  foreign  material  may  be  added. 
A  good  idea  of  the  form  of  adulteration  may  usually  be  gained 
from  the  relation  between  the  fat  and  the  solids  not  fat.  In 
watered  milk  both  of  these  are  low,  but  the  ratio  between  them 
is  about  the  same  as  in  normal  milk.  In  skimmed  milk  the 
solids  not  fat  may  be  nearly  normal  while  the  fat  is  very  low. 
If  the  total  solids  and  the  solids  not  fat  are  both  below  standard, 

*  Van  Slyke  and  Hart:  Am.  Chem.  J.,  29  (igo^),  170. 


food:  analytical  methods:   milk.  185 

while  the  proportion  of  fat  to  solids  not  fat  is  very  small,  it  is 
a  fair  assumption  that  the  milk  is  both  skimmed  and  watered. 

Leach  *  states  that  it  is  nearly  always  safe  to  condemn  a 
milk  as  watered,  if  the  total  solids  are  below  10.75  per  cent., 
with  a  corresponding  amount  of  fat. 

Direct  Determination  of  Added  Water. — This  may  be  done 
by  determining  the  specific  gravity  of  the  milk-serum  after 
coagulation  and  removal  of  the  casein. I  The  casein  is  coag- 
ulated by  dilute  acetic  acid,  filtered  off  on  a  dry  filter,  and 
the  specific  gravity  of  the  filtrate  taken  at  15°  C.  by  the  West- 
phal  balance.  The  specific  gravity  of  the  serum  from  normal 
milk  is  never  below  1.027,  ^^^  only  rarely  below  I.029.  The 
addition  of  each  ten  per  cent,  of  water  lowers  tne  specific 
gravity  by  o.ooio  to  0.0035. 

A  more  convenient  method  of  determination  is  Dv  the  Zeiss 
immersion  refract ometer  if  this  instrument  is  available.  (See 
Bur.  of  Chem.,  Bui.  107  (Revised),  p.  120;  also  JLeacn,  Food 
Inspection  and  Analysis,  p.  766.)  The  Abbe  reiractometer, 
page  202,  can  also  be  used. 

The  determination  is  often  of  importance  since  it  enables 
the  analyst  to  distinguish  readily  between  milk  which  is  directly 
adulterated  on  the  one  hand,  and  that  which  is  only  below 
standard  on  the  other.  In  legal  prosecutions  the  amount  of 
penalty  imposed  is  sometimes  dependant  on  whether  the  analyst 
can  show  evidence  of  the  actual  addition  of  water. 

Cane-sugar. — To  detect  the  presence  of  cane-sugar  boil 
about  10  c.c.  of  the  milk  with  o.i  gram  of  resorcin  and  i  c.c. 
of  hydrochloric  acid  for  five  minutes.  The  liquid  wiU  be 
colored  rose-red  if  cane-sugar  be  present.  The  quantitative 
determination   may   be   made   by   means   of   the   polariscope. 

*  "Food  Inspection  and  Analysis." 

t  Woodman:   J.  Am.  Chem.  Soc,  21  (1899),  503;    Leach:    "Food  Inspection 
and  Analysis,"  p.  765. 


180  AIR,   WATER,    AND   FOOD. 

Cane  sugar  is  occasionally  found  in  the  milk  through  the  use 
of  diluted  condensed  milk  to  eke  out  the  supply. 

Starch. — Heat  lo  c.c.  of  the  milk  to  boiling  in  a  test-tube, 
and  when  cold  add  a  few  drops  of  the  solution  of  iodine  in 
potassium  iodide.  The  presence  of  even  0.2  per  cent,  of  starch 
will  be  shown  by  the  characteristic  blue  coloration. 

Coloring-matters. — The  principal  coloring-matters  added 
to  milk  are  annatto,  caramel,  and  coal-tar  dyes.  In  general, 
coloring-matters  are  added  only  to  watered  milk,  but 
general,  coloring-matters  are  added  only  to  watered  milk,  but 
occasionally  samples  w^hich  w^ere  of  standard  quality  have 
been  found  to  be  colored. 

Directions . — Put  about  100  c.c.  of  the  milk  into  a  small 
beaker,  add  2  c.c.  of  25  per  cent,  acetic  acid  and  allow^  the 
beaker  to  stand  quietly  for  about  ten  or  fifteen  minutes  in 
a  water-bath  kept  at  70°  C,  the  casein  being  thus  separated 
as  a  compact  cake.  Decant  off  the  whey,  squeezing  the 
curd  as  free  from  it  as  possible  by  means  of  a  spatula.  Trans- 
fer the  curd  to  a  flask  and  let  it  remain  covered  w4th  ether 
for  an  hour  or  more. 

Evaporate  the  ether  extract,  which  contains  the  annatto 
if  present,  add  5  c.c.  of  water,  and  dilute  sodium  hydroxide 
until  the  mixture,  after  thorough  beating  and  stirring  wath 
a  glass  rod  is  faintly  alkaline  tc  litmus  paper,  and  filter 
through  a  wet  filter.  If  annatto  is  present,  it  w^ill  permeate 
the  filter  and  give  it  an  orange  color  w^hen  the  fat  is  w-ashed 
off  under  the  tap.  Treat  the  filter  with  stannous  chloride. 
If  annatto  is  present,  a  pink  color  will  be  produced. 

After  pouring  off  the  ether  examine  the  milk-curd  for 
caramel  or  aniline  orange.  If  the  curd  is  left  white,  neither 
of  these  colors  is  present.  If  caramel  has  been  used,  the 
curd  will  be  of  a  pinkish-brown  color;  if  the  color  is  due  to 
the  aniline  dye,  the  curd  will  have  a  yellow  or  orange  tint 
In  doubtful  cases  the  curd  should  be  compared  with  one  from  a 


food:  analytical  methods:  milk.  187 

milk  known  to  be  uncolored.  To  distinguish  between  the  two 
colors  shake  a  small  portion  of  the  curd  in  a  test-tube  with 
strong  hydrochloric  acid.  The  caramel-colored  curd  will  act 
similarly  to  an  imcolored  curd,  that  is,  it  will  gradually  produce 
a  deep  blue  color  in  the  solution.  On  the  other  hand,  the 
coal-tar  color  will  immediately  produce  with  the  hydrochloric 
acid  a  pink  color. 

Note. — It  is  to  be  regretted  that  there  is  no  positive  test 
for  caramel  sufficiently  delicate  to  serve  here.  The  test  as 
described  is  a  negative  one,  the  only  indication  of  caramel  being 
the  occurrence  of  a  colored  curd  in  which  the  color  is  not  given 
by  the  coal-tar  dye. 

Preservatives. — The  preservatives  usually  added  to  milk 
are  formaldehyde  and  borax  or  boric  acid.  Carbonate  of  soda 
is  added  in  some  cases  to  disguise  the  acidity  of  sour  milk. 

Formaldehyde. — This  is  generally  used  as  a  40  per  cent, 
aqueous  solution,  sold  under  the  name  of  formalin.  Several 
simple  tests  commonly  used  for  the  detection  of  formaldehyde 
will  be  described. 

(i)  When  the  sulphuric  acid  is  added  to  the  milk  in  making 
the  Babcock  test  for  fat,  a  bluish- violet  ring  will  be  noticed 
at  the  junction  of  the  two  liquids  when  formaldehyde  is  present. 
One  part  of  formaldehyde  in  200,000  parts  of  milk  can  be 
detected  by  this  test,  but  it  fails  when  the  formaldehyde  amounts 
to  0.5  per  cent.  The  test  is  more  delicate  if  the  sulphuric  acid 
contains  a  trace  of  ferric  chloride. 

(2)  To  10  c.c.  of  milk  in  a  small  porcelain  dish  add  an  equal 
volume  of  hydrochloric  acid  (1.20  sp.  gr.).  Add  one  drop 
of  ferric  chloride  solution  and  heat  the  dish  with  a  small  flame, 
stirring  vigorously,  until  the  contents  are  nearly  boiling. 
Remove  the  flame  and  continue  the  stirring  for  two  or  three 
minutes,  then  add  about  50  c.c.  of  water.  The  presence  of 
formaldehyde  will  be  shown  by  a  violet  color  which  appears  in 


1 88  AIR,    WATER,   AND  FOOD. 

the  particles  of  the  precipitated  casein,  the  depth  of  color 
depending  on  the  amount  of  formaldehyde  present.  The  color 
should  be  observed  carefully  at  the  moment  of  dilution.  This 
test  readily  shows  the  presence  of  one  part  of  formaldehyde  in 
250,000  parts  of  milk,  if  fresh. 

Boric  Acid  or  Borax. — Make  25  c.c.  of  the  milk  distinctly 
alkaline  with  lime  water  and  evaporate  to  dryness  on  the 
water  bath.  Char  the  residue  over  a  flame  but  do  not  neces- 
sarily heat  it  until  white.  Digest  the  residue  with  15-20  c.c. 
of  water  and  add  hydrochloric  acid  (1.12)  until  the  mixture 
is  faintly  acid  to  litmus  paper.  Filter,  and  add  i  c.c.  of  acid 
in  excess.  Place  a  strip  of  turmeric  paper  in  the  solution  and 
evaporate  to  dryness  on  the  water  bath.  If  boric  acid  or  borates 
are  present,  the  paper  takes  on  a  peculiar  red  color,  which  is 
changed  by  ammonia  to  a  dark  blue-green,  but  is  restored  by 
acid.  Excess  of  hydrochloric  acid  should  be  avoided,  as  it 
turns  the  paper  a  dirty  green  when  evaporated.  This  test 
can  also  be  applied  to  the  hydrochloric  acid  solution  of  the  ash. 

Sodium  Carbonate, — Detected  in  the  milk-ash,  as  on  page 
174.  If  effervescence  occurs,  test  the  original  milk  with  rosolic 
acid  as  follows:  Mix  10  c.c.  of  milk  with  an  equal  volume  of 
alcohol,  and  add  a  few  drops  of  a  one  per  cent,  solution  of 
rosolic  acid.  The  presence  of  sodium  carbonate  is  indicated 
by  a  more  or  less  distinct  pink  coloration.  A  comparative 
test  should  be  made  at  the  same  time  with  milk  known  to  be 
pure. 

CONDENSED   MILK. 

It  may  in  some  cases  afford  an  interesting  variation  to 
carry  out  the  tests  on  condensed  milk,  this  having  within  recent 
years  become  an  important  article  of  food.  With  the  unsweet- 
ened condensed  milk,  commonly  sold  as  "  evaporated  milk," 
the  methods  as  used  with  whole  milk  can  be  applied  directly  to 


food:  analytical  methods:  milk. 


189 


the  diluted  sample.  In  the  case  of  sweetened  condensed  milk, 
which  is  usually  meant  by  the  term  condensed  milk  in  this 
country,  the  methods  must  in  some  cases  be  modified,  on 
account  of  the  large  proportion  of  cane  sugar  present. 

The   following   are   analyses  of   a   few   typical  samples   of 
sweetened  condensed  milk: 


COMPOSITION    OF   SWEETENED    CONDENSED   MILK. 


Total 
Solids. 

Water. 

Milk 
Solids. 

Cane- 
sugar. 

Lac- 
tose. 

Pro- 
tein. 

Fat. 

Ash. 

Degree 
of 
Con- 
densa- 
tion. 

Fat  In 
Origi- 
nal 
MVlk. 

2^ 

3' 

72.95 
71-03 
71-58 

27.05 
28.97 
28.42 

30.01 

27-49 
24.24 

42-94 
43-45 
47-34 

11.28 
11.78 
13.08 

7-85 
7-51 
9.04 

9-3 
6.6 
0.15 

1.58 
1.60 

1-97 

2.26 
2.29 
2.8 

4. II 

2.88 
0.05 

*  Normal. 


*  Not  made  from  standard  milk. 


Condensed  from  skimmed  milk. 


Preparation  of  the  Sample. — Transfer  the  entire  contents  of 
the  can  to  a  large  evaporating  dish,  scraping  it  out  clean,  and 
work  it  thoroughly  with  a  pestle  until  homogeneous.  Weigh 
out  40  grams  of  the  mixed  sample  and  dilute  to  100  c.c.  in  a 
calibrated  flask. 

Total  Solids. — Dilute  10  c.c.  of  the  40  per  cent,  solution  with 
an  equal  volume  of  water  and  evaporate  5  c.c.  of  the  diluted 
mixture,  corresponding  to  i  gram  of  the  sample,  to  dryness  in 
a  weighed  platinum  dish,  as  directed  on  page  173.  It  is  of 
importance  to  have  the  sample  very  dilute  in  order  to  get  an 
accurate  determination  of  the  solids  and  this  can  best  be 
accomplished  in  the  manner  described. 

Ash. — Ignite  the  residue  from  the  determination  of  total 
solids,  as  in  the  case  of  ordinary  milk. 

Fat. — The  fat  is  the  determination  of  most  importance  since 
judgment  of  the  quality  of  the  sample  is  based  m.ore  largely  on 
this  factor  than  on  any  other.     Its  determination,  however,  is 


IpO  AIR,    WATER,    AND   FOOD. 

attended  with  some  difficulty  on  account  of  the  large  amount  of 
cane  sugar  present.  The  Babcock  method,  for  instance,  does 
not  give  satisfaction  since  the  charring  of  the  sugar  by  the 
sulphuric  acid  prevents  a  clean  separation  of  the  fat.  The 
Adams  method,  moreover,  is  unreliable  because  the  cane  sugar 
dries  on  the  paper  coil,  enclosing  the  fat  so  that  it  is  not  readily 
extracted  by  the  solvent.  Several  modifications  of  these 
methods  have  been  proposed,  however,  by  which  fairly  good 
results  may  be  obtained. 

Babcock  Method  as  modified  by  Leach. — Leach  has  modified 
the  Babcock  test  so  as  to  make  it  available  for  sweetened  con- 
densed milk  by  precipitating  the  proteids  and  fat  with  copper 
sulphate  and  then  removing  the  interfering  sugar  by  several 
extractions  with  water.  Directions  for  carrying  out  the  test 
will  be  found  in  Leach:  Food  Inspection  and  Analysis,  p.  149, 
or  in  Bur.  of  Chem.,  Bui.  107,  p.  123. 

Adams  Method. — This  can  be  applied  in  the  following 
manner:  Dry  5  c.c.  of  the  40  per  cent,  solution  on  the  paper 
coil,  as  described  on  page  175.  Extract  with  petroleum  ether 
in  the  usual  manner;  dry,  soak  the  coil  in  500  c.c.  of  water  for 
several  hours;  dry,  extract  again  for  five  hours  and  weigh  the 
fat  as  usual. 

Gottlieb  Method. — Use  10  c.c.  of  the  40  per  cent,  solution 
and  carry  out  the  determination  exactly  as  described  on  page 
178.  In  many  ways  this  method  will  be  found  to  give  the  best 
results  on  condensed  milk. 

Proteids. — Determine  nitrogen  in  5  c.c.  of  the  40  per  cent, 
solution  and  multiply  by  6.38. 

Lactose. — Use  the  method  described  on  page  181  on  25  c.c. 
of  the  40  per  cent,  solution. 

Cane  Sugar. — This  may  be  determined  with  sufficient 
accuracy  for  most  purposes  by  difference,  subtracting  the  milk 
solids  (the  sum  of  the  lactose,  fat,  protein  and  ash),  from  the 


food:  analytical  methods:  milk.  191 

total  solids.  The  direct  estimation  of  the  cane  sugar  in  the 
presence  of  lactose  may  be  carried  out  with  the  polariscope 
by  the  choice  of  a  suitable  inverting  agent.  The  writer  has 
obtained  good  results  by  inversion  with  acid  mercuric  nitrate, 
as  described  by  Harrison.* 

BUTTER. 

General  Statements. — Butter  consists  of  the  fat  of  milk, 
together  with  a  small  percentage  of  w^ater,  salt,  and  curd. 
The  curd  is  made  up  principally  of  the  casein  of  the  milk. 
These  various  ingredients  are  present  in  about  the  following 
proportions : 

Fat 78.00-90.0  per  cent. ;  average,  82  per  cent. 

Water 5.00-20.0     "      "  "         12 

Salt 0.40-15.0     ''       ''  "  5     " 

Curd o.ii-  5-3     "      "  "  I     "        " 

The  fat  consists  of  a  mixture  of  the  glycerides  of  the 
fatty  acids.  The  characteristic  feature  of  butter-fat  is  the 
extraordinarily  high  proportion  of  the  glycerides  of  the  solu- 
ble and  volatile  fatty  acids  when  contrasted  with  other  fats. 

Ti  e  following  may  be  taken  as  the  probable  composition 
of  normal  butter-fat: 

Acid.  Per  cent.  Acid.         Per  cent.  Triglycerides. 

Dioxystearic i-oo  1.04 

Oleic 32-50  33-95 

Stearic 1.83  1.91 

Palmitic 38.61  40.51 

Myristic 9-89  i°-44 

Laurie 2.57  2.73 

Capric 0.32  0.34 

Caprylic 0.49  0.53 

Caproic 2.09  2.32 

Butyric 5-45  ^-23 

Total 94.75  100.00 

According  to  this,  the  proportion  of  volatile  acids  in  butter 
(butyric,  caproic,  capryhc,  and  capric  acids)  amounts  to  8.35%. 
The  amount  of  volatile  acid  in  lard,  for  example,  is  about  0.1%. 

■-Analyst,  29,  248.  t  Browne,  /.  Am.  Chem.  Soc,  21  [1899),  807. 


192  AIR,  WATER,    AND    FOOD. 

The  usual  examination  of  butter  consists  in  the  examina- 
tion of  the  butter-fat,  in  order  to  detect  the  presence  of 
foreign  fats.  The  determination  of  the  amount  of  curd  may 
be  of  value  also  in  some  cases,  more  especially  from  a 
sanitary  standpoint.  The  chief  danger  to  health  probably 
lies  in  the  possible  decomposition  of  the  nitrogenous  portion, 
for  it  is  quite  generally  recognized  that  the  substitution  of 
oleomargarine  is  not  injurious  to  health.  It  is  a  not  infre- 
quent practice,  however,  as  remarked  in  the  previous  chap- 
ter, to  incorporate  a  large  amount  (sometimes  as  high  as 
^T,  per  cent.)  of  curd  and  other  nitrogenous  matters  in  fresh 
butter.  If  this  is  kept  for  any  length  of  time,  a  decomposi- 
tion is  liable  to  occur  which  may  have  serious  effects.  Other 
determinations  that  are  usually  made  are  the  w^ater  and  salt. 
The  term  "  oleomargarine  "  is  usually  applied  to  a  mixture 
of  refined  lard,  "  oleo  oil,"  which  is  mainly  the  olein  of  beef  fat, 
and  cottonseed  oil.  Ordinarily  a  small  proportion  of  butter 
is  added  and  the  product  is  generally  churned  with  milk. 

A  comparatively  recent  form  of  butter  substitute  which 
finds  extensive  use  in  some  sections  of  the  country  is 
*' process,"  or  "renovated,"  butter.  The  raw  material,  or 
"stock,"  used  for  the  manufacture  of  this  consists  of  butter 
which  cannot  be  sold  as  butter  either  because  of  deteriora- 
tion through  rancidity  or  moulding  or  because,  through  care- 
lessness on  the  part  of  the  makers,  it  possesses  an  unattractive 
appearance  or  flavor.  The  chief  recruiting-ground  for  this 
material  is  the  country  grocery  store.  The  fat,  separated 
from  the  curd  by  melting  and  settling,  is  aerated  to  remove 
disagreeable  odors  and  leave  it  nearly  neutral.  This  is  then 
emulsified  with  fresh  milk  which  has  been  inoculated  with 
a  bacterial  culture,  and  the  whole  is  chilled,  granulated, 
and  churned.  The  butter  is  then  worked  and  packed  for 
market  in  the  usual  manner.     The  character  of  the  prod- 


food:  analytical  methods:  butter.  193 

uct  has  much  improved  since  the  early  days  of  the 
industry,  the  best  grades  now  approximating-  the  lower 
grades  of  creamery  butter. 

The  ''  aroma  "  of  butter  seems  to  be  connected  with  the 
decomposition  produced  by  the  action  of  bacteria  on  the 
casein  and  the  small  amount  of  milk-sugar  that  is  present, 
and  not  with  any  change  in  the  fats;  there  is  no  evidence, 
however,  that  any  unwholesome  effect  is  produced  by  the 
aroma-giving  organisms. 

The  rancidity  of  butter-fat  is  generally  considered  to  be 
due  to  decomposition  and  oxidation  of  the  fatty  acids,  espe- 
cially the  unsaturated  ones,  the  amount  of  change  depending 
on  conditions  of  light,  heat,  and  exposure  to  air. 

Examination  of  the  Fat.  —  The  fat  is  first  separated 
from  the  other  constituents  of  the  butter  so  that  it  may  be 
weighed  out  for  the  various  tests. 

Directions. — Melt  a  piece  of  butter,  about  two  cubic 
inches,  in  a  small  beaker  placed  on  top  of  the  water-bath  so 
that  the  temperature  shall  not  rise  above  50°-6o°.  After 
about  fifteen  minutes  the  water,  salt,  and  curd  will  have  set- 
tled to  the  bottom.  (A  better  separation  may  be  secured 
by  dividing  the  melted  sample  equally  between  two  test-tubes 
and  whirling  them  for  3-4  minutes  in  a  centrifugal  machine.) 
Place  a  bit  of  absorbent  cotton  in  a  funnel,  previously  waimed, 
and  decant  off  the  clear  fat  through  the  cotton  into  a  second 
beaker,  taking  care  that  none  of  the  water  or  curd  is  brought 
upon  the  filter.  When  the  filtered  fat  has  cooled  to  about  40° 
place  a  small  pipette  in  the  beaker  and  weigh  the  whole. 

By  means  of  the  pipette  the  desired  amount  of  fat  is  taken 
out,  the  pipette  replaced  in  the  beaker,  and  the  whole  again 
weighed.  The  difference  in  weight  gives  the  exact  amount 
of  fat  taken.  It  is  a  saving  of  time,  however,  if  several  por- 
tions are  to  be  weighed  out,  to  make  the  weights  one  after 


194 


AIR,    WATER,    AND    FOOD. 


another,  so  that  one  weight  will  suffice  for  a  determination. 
Weigh  out  thus  :  Two  portions  of  5  grams  each  into  250-c.c. 
round-bottomed  flasks  for  the  Reichert-Meissl  method,  one 
portion  of  25  to  3  grams  into  a  500-c.c.  beaker  for  Hehner's 
process,  two  portions  of  about  .35  to  .5  gram  each  into  300-c.c. 
-glass-stoppered  bottles  for  determination  of  the  iodine  value. 
In  the  case  of  the  larger  portions,  weigh  only  to  the  nearest 
milligram. 

(i)  Reichert-Meissl  Number  for  Volatile  Fatty  Acids. 
— Directions. — To  the  fat  in  the  250-c.c.  flasks  add  2  c.c.  of 
strong  caustic  potash  (1:1)  and  10  c.c.  of  95  per  cent, 
alcohol.  Connect  the  flask  with  a  return-flow  condenser 
and  heat  on  a  water-bath  so  that  the  alcohol  boils  vigorously 
for  25  minutes.  At  the  end  of  this  time  disconnect  the  flask 
and  evaporate  ofT  the  alcohol  on  a  boiling-water  bath.  After 
the  complete  removal  of  the  alcohol  add  140  c.c.  of  re- 
cently boiled  distilled  water  which  has  been  cooled  to  about 
50°.  The  water  should  be  added  slowly,  a  few  cubic  centi- 
meters at  a  time.  Warm  the  flask  on  the  water-bath  until 
a  clear  solution  of  the  soap  is  obtained.  Cool  the  solution  to 
about  60°  and  add  8  c.c.  of  sulphuric  acid  (1:4)  to  set  free 
.the  fatty  acids.  Drop  two  bits  of  pumice,  about  the  size  of 
a  pea,  into  the  flask,  close  it  by  a  well-fitting  cork,  which  is 
tied  in  with  twine,  and  immerse  it  in  boiling  water  until  the 
fatty  acids  have  melted  to  an  oily  layer  floating  on  the  top 
of  the  liquid.  Cool  the  flask  to  about  60°,  remove  the  cork, 
and  immediately  attach  the  flask  to  the  condenser. 

Distil  no  c.c.  into  a  graduated  flask  in  as  nearly  thirty 

.minutes  as  possible.     Thoroughly  mix  the  distillate,  pour  the 

whole  of  it  through  a  dry  filter,  and  titrate  100  c.c.  of  the 

N  . 

mixed  filtrate  with   —     sodium    hydroxide,    using    phenol- 

phthalein  as  an  indicator.   Multiply  the  number  of  cubic  centi- 


food:  analytical  methods:  butter.  195 

meters  of  alkali  used  by  eleven-tenths,  and  correct  the  reading 

also  for  any  weight  of  fat  greater  or  less  than  5  grams. 

For  example,  if  5.3  grams  of  butter-fat  are  used,  and  100 

N 
ex.  of  the  distillate  require   27.4  c.c.  ol  —  NaOH,   no  c.c. 

would  require  27.4x15=30.14  c.c.  Then  5.3  :  30.14  = 
5  :  X  .  x=-2d>.^.     X  is  the  Reichert-Meissl  number. 

Xotes. — The  Reichert-Meissl  number  for  genuine  butter 
varies  from  24  to  34;    the  average  usually  taken  is  28.8. 

Cocoanut  oil  gives  a  value  of  6-8;  other  edible  fats  and  oils 
have  a  value  usually  less  than  i. 

The  presence  of  cocoanut  oil  is  readily  shown  by  the  Reichert- 
Meissl  number  taken  in  connection  with  the  saponification 
value,  that  is,  the  number  of  milligrams  of  potassium  hydroxide 
required  to  saponify  one  gram  of  the  fat.  (For  a  description 
of  the  method  of  determining  this  see  Lewkowitsch:  Oils,  Fat, 
and  Waxes,  or  Gill:  A  Short  Handbook  of  Oil  Analysis).  The 
Reichert-Meissl  number  is  higher  in  butter  fat  than  in  cocoanut 
oil,  while  the  saponification  value  is  lower.  In  pure  butter 
fat  the  value  of  the  expression  (Saponification  value — Reichert- 
Meissl  number — 200)  varies  from  3.4  to  4.1;  in  pure  cocoanut 
oil  it  runs  from  47  to  50.7.* 

When  the  fat  is  treated  with  potash  it  is  decomposed,  the 
glycerine  being  set  free,  and  the  potassium  salts  of  the  fatty 
acids,  that  is  to  say,  the  potassium  soaps  are  formed.  Hence 
the  process  is  called  saponification.  For  butyric  acid  the 
reaction  may  be  expressed 

C3H,(C3H,COO)3  +  3KOH  =  sCsH.COOK  +  C3H/OH)3. 

The  alcohol  is  used  to  dissolve  the  fat.  But  at  the 
moment  the  butyric  acid  is  set  free  it  tends  to  combine  with 
the  alcohol  to  torm  a  volatile  ether: 

C3H,C00H  +  C,H,OH  =  QH.COOQH^  +  HA 

*  Juckenack  and  Pasternack:    Ztschr.  Nahr.  Geniissm.,  7  {1904),  193. 


196  AIR,    WATER,    AND    FOOD. 

The  object  of  the  return-flow  condenser  is  to  prevent  the 
escape  of  this  volatile  ether  and  to  allow  of  its  complete 
saponification. 

If  the  water  used  to  dissolve  the  soap  is  added  too  rap- 
idly, the  soap  may  be  decomposed  with  the  liberation  o'  the 
fatty  acids:   C3H7  COOK  +  H^O  =  C3H,  COOH  +  KOH. 

The  fatty  acids  are  set  free  at  the  proper  time  by  means 
of  sulphuric  aci:\  and  the  volatile  acids  distilled  off  and 
titrated.     The  pumice  is  added  to  prevent  explosive  boiling. 

The  whole  of  the  volatile  acids  do  not  pass  over  into  the 
distillate,  but  only  a  part,  the  amount  depending  upon  the 
rate  of  distillation  and  tlie  volume  of  the  distil;ate  Hence,  m 
order  to  get  uniform  results,  it  is  necessary  to  follow  the  pre- 
scribed procedure  with  threat  care. 

(2)  Hehner's  Method  for  Direct  Determination  of 
the  Fixed  Fattv  Acids. — Directions. — To  the  portion  of 
2.5  grams  weighed  out  into  the  500-c.c.  beaker  add  J  c.c.  of 
caustic  potash  and  20  c.c.  of  95  per  cent,  alcohol.  Cover 
the  beaker  with  a  watch-glass  and  heat  it  on  the  water-bath 
until  the  liquid  is  clear  and  homogeneous.  As  it  is  not  essen- 
tial to  prevent  the  escape  of  the  volatile  acids,  the  use  01' a. 
return-flow  condenser  is  not  necessary.  Evaporate  off  the 
alcohol  on  the  water-bath  and  dissolve  the  soap  in  about 
400  c.c.  of  w^arm  distilled  water.  When  the  soap  is  com- 
pletely dissolved  add  10  c.c.  of  hydi'ochloric  acid  (sp.  gr. 
I.I 2),  and  heat  the  beaker  in  the  water-bath  almost  to  boil- 
ing until  the  clear  oil  floats.  Meanwhile  dry  and  weigh  a 
thick  filter  in  a  small  covered  beaker.  Allow  the  solution 
to  cool  until  the  fat  forms  a  solid  cake  on  top ;  filter  the  clear 
liquid  and  finally  bring  the  solid  fats  upon  the  weighed 
filter.  Wash  the  beaker  and  fat  thoroughly  with  cold  water, 
then  wash  out  the  fat  adhering  to  the  beaker  with  boiling 
water,  which  is  poured  through  the  filter,  taking  care  that 


food:  analytical  methods:  butter.  197 

the  filter  is  never  more  than  two-thirds  full.  If  the  filter  paper 
is  of  good  texture  and  thoroughly  wet  beforehand  it  will  retain 
the  fatty  acids  completely.  If,  however,  oily  particles  are 
noticed  in  the  filtrate,  cool  it  by  adding  pieces  of  ice,  remove 
the  solidified  particles  with  a  glass  rod  and  transfer  them  to 
the  filter.  Cool  the  funnel  by  plunging  it  into  cold  water, 
remove  the  filter,  place  it  in  the  weighing-beaker  and  dry  it  at 
100°  to  constant  weight.  The  fat  should  be  heated  about  an 
hour  at  first,  then  for  periods  of  about  thirty  minutes,  until  the 
weight  is  constant  within  2  mgs. 

Notes. — 87.5  per  cent,  is  usually  taken  as  the  proportion 
of  fixed  fatty  acids  in  butter-fat ;  88  and  89  per  cent,  have 
been  frequently  found.  All  other  fats  yield  from  95  to  96 
per  cent,  of  insoluble  fatty  acids. 

(3)  Determination  of  Iodine  Value. — This  method  is 
based  on  the  fact  that  certain  of  the  fatty  acids,  notably 
the  "unsaturated  acids,"  as  oleic  acid,  C17H33COOH,  take 
up  the  halogens  with  the  formation  of  addition  products. 

Directions. — Dissolve  the  fat  in  the  300-c.c.  bottles  in 

10  c.c.  of  chloroform.     Add  30  c.c.  of  the  iodine  solution 

from  a  pipette  or  glass-stoppered  burette,  and  allow^  the 

l)ottles  to  stand  with  occasional  shaking  for  fifteen  minutes. 

Add  10  c.c.  of  20  per  cent,  potassium  iodide  solution,  then 

100  c.c.  of  distilled  w^ater,  and  titrate  the  excess  of  iodine 

N 
with  —   sodium  thiosulphate  until  the  solution  is  faintly 

yellow.  Add  2-3  c.c.  of  starch  solution  and  titrate  to 
the  disappearance  of  the  blue  color.  Calculate  the  result 
in  grams  of  iodine  absorbed  by  100  grams  of  fat.  This  is 
called  the  Iodine  Number,  or  Iodine  Value. 

At  the  time  of  making  the  determination  carry  out  two 
*' blanks  "  in  exactly  the  same  way  except  that  no  fat  is  used 
and  only  20  c.c.  of  the  iodine  solution  is  added. 

Standardization  of  the  Thiosulphate  Solution. — As  this  is 


198  AIR,    WATER,    AND    FOOD. 

not  permanent,  its  strength  should  be  determined  by  means 
of  the  standard  potassium  bichromate  solution,  i  c.c.  of 
which  is  equivalent  to  0.0 1  gram  of  iodine. 

Measure  20  c.c.  of  the  potassium  bichromate  from  a 
pipette  into  an  Erlenmeyer  flask.  Add  5  c.c.  of  potassium 
iodide,  100  c.c.  of  w^ater,  and  5  c.c.  of  strong  hydrochloric 
acid.  Titrate  the  liberated  iodine  with  the  thiosulphate  solution 
until  the  color  has  almost  disappeared,  then  add  starch  solution 
and  continue  the  titration  until  the  blue  color  changes  to  a 
sea-green,  due  to  the  formation  of  chromium  chloride.  The 
iodine  is  liberated  in  accordance  with  the  following  equation: 

K.Crp,  +  1 4HCI  +  6KI  =  8KC1  +  2CrCl3  +  yHp  +  6L 

Calculation  of  Results. — Example. — From  the  standardi- 
zation, 

16.07  c.c.  thiosulphate  =  20  c.c.  bichromate  =0.200  gram  I; 
I  c.c.  thiosulphate  =0.0125  gram  L 
Also,  from  blank, 

20  c.c.  iodine  solution  =42.40  c.c.  thiosulphate; 
I  c.c.  iodine  solution  =  2.12  c.c.  thiosulphate. 
If  30  c.c.  iodine  solution  have  been  added  to  0.6542 
grams  of  fat,  then  30X2.12=63.60  c.c.  is  the  equivalent 
amount  of  thiosulphate  solution;  and  if  44.85  c.c.  thio- 
sulphate were  used  to  titrate  excess  of  free  iodine,  63.60  — 
44.85  =  18.75  c.c.  is  the  amount  of  thiosulphate  equivalent 
to  the  iodine  combined  with  the  fat.  Then,  since  i  c.c. 
thiosulphate   is    equivalent    to   0.0125    gram   free    iodine, 

18. 75X0. 0125  „  r    •     J-  -u-        J        -.1 

-^^ ^X  100  =  35.83  grams  of  lodme  combmed  with 

100  grams  fat. 

Notes. — It  is  assumed  that  100  grams  of  pure  butter-fat 
absorb  30-40  grams  iodine;  oleomargarine,  63-75  grams; 
olive-oil,  83  grams;    and  cottonseed-oil,   106  grams. 


food:   analytical  methods:  butter.  199 

The  products  formed  by  the  action  of  iodine  on  the  fats 
are  mainly  addition  products  with  a  slight  proportion  of 
substituted   bodies.     Thus   the   unsaturated   olein, 

(Q,H33COO)3C3H„ 

takes  up  six  atoms  of  iodine,  forming  an  addition  product, 
di-iodo-stearin,   (Ci7H33l2COO)3C3H5. 

The  method  in  general  use  for  determining  the  iodine 
value  of  fats  and  oils  has  been  that  of  Baron  Hiibl,*  an 
alcoholic  solution  of  iodine  and  mercuric  chloride  being 
used  as  the  reagent.  The  method  here  described,  due  to 
Hanust,  has  the  advantage  that  the  solutions  keep  better, 
remaining  practically  unchanged  for  several  months,  and 
that  the  action  is  about  sixteen  times  as  rapid.  For  the 
fats  and  for  oils  with  low  iodine  values  the  results  are  very 
close  to  the  figures  obtained  by  the  Hubl  process.  If  it  is 
desired  to  carry  out  the  determination  by  the  older  method, 
directions  can  be  found  in  any  standard  work  on  the  analysis 
of  oils. 

Great  care  should  be  taken  that  there  is  no  change  in 
temperature  between  the  time  of  measuring  the  solution  of 
iodine  for  the  blanks  and  for  the  determinations,  since  the 
high  coefficient  of  expansion  of  acetic  acid  may  cause  a  material 
error. 

The  Spoon  Test  or  "  Foam  ''  Test.— Melt  a  piece  of  the 
sample  as  large  as  a  small  chestnut  in  an  ordinary  tablespoon 
or  a  small  tin  dish.  A  test-tube  can  be  used  if  desired.  Use 
a  small  flame  and  stir  the  melting  fat  with  a  splinter  of  wood 
(such  as  a  match).     Then  increase  the  heat  so  that  the  fat 

*  Ditig.  Poly.  J.,  253,  281;    /.  Soc.  Chem.  Ind.,  3  {1884),  641. 
f  Ztschr.  Unters.  Nahr.  u.  Genussm.,  4  (ipoi),  913. 


200  AIR,    WATER,    AND    FOOD. 

shall  boil  briskly,  and  stir  thoroughly,  not  neglecting  the  outer 
edges,  several  times  during  the  boiling. 

Oleomargarine  and  renovated  butter  boil  noisily,  usually 
sputtering  like  a  mixture  of  grease  and  water  when  boiled, 
and  produce  little  or  no  foam.  Genuine  butter  usually  boils 
with  much  less  noise  and  produces  an  abundance  of  foam. 
The  difference  in  regard  to  the  foam  is  very  marked. 

Note  also  the  appearance  of  the  particles  of  curd  after  the 
boiling.  With  genuine  butter  these  will  be  very  small  and  finely 
divided,  hardly  noticeable  in  fact,  while  with  oleomargarine 
and  renovated  butter  the  curd  gathers  in  much  larger  masses 
or  lumps. 

Notes. — This  simple  method  is  of  value  for  giving  a  quick 
decision  regarding  a  sample,  and  is  especially  useful  for  the 
detection  of  renovated  butter.  The  differences  in  the  composi- 
tion of  butter-fat  brought  about  by  renovation  are  so  slight 
that  chemical  methods  are  here  of  no  avail. 

The  spoon  test,  however,  will  distinguish  in  the  great 
majority  of  cases  between  genuine  butter  on  the  one  hand  and 
oleomargarine  and  renovated  butter  on  the  other;  the  index 
of  refraction  or  the  chemical  methods  just  described  readily 
distinguish  between  the  two  latter. 

Physical  Methods. — Microscopic  Examination. — Pure,  fresh 
butter  is  not  ordinarily  crystalline  in  structure.  Butter  which 
has  been  melted,  however,  and  fats  which  have  been  liquefied 
and  allowed  to  cool  slowly  show  a  distinct  crystalline  structure, 
especially  by  polarized  light.  If  only  fresh  butter  were  sold, 
and  all  adulterants  had  been  previously  melted  and  slowly 
cooled,  this  method  would  be  all  that  would  be  necessary  for 
the  detection  of  adulteration.  As  it  is,  however,  it  is  most 
useful  in  makmg  comparative  examinations  of  samples  which 
have  been  subjected  to  the  same  conditions.  From  an  examina- 
tion of  the  accompanying  plate,*  which  shows  the  appearance 

♦From  photomicrographs  by  A.  G.  Woodman  and  A.  I.  Kendall,  1900. 


food:  analytical  methods:  butter.  201 

by  polarized  light  of  four  samples  of  known  origin  which  were 
melted  and  cooled  slowly  under  exactly  similar  conditions,  it 
will  be  seen  that,  while  the  differences  are  noticeable,  they  are 
not  sufficient  in  all  cases  to  form  a  basis  for  absolute  identi- 
fication. 

About  the  most  that  can  be  said  is  that  if  a  small  bit,  about 
the  size  of  a  pin-head,  of  the  fresh,  unmelted  sample,  is  taken 
from  the  center  of  the  mass  and  pressed  out  on  a  slide  by  gentle 
pressure  on  the  cover  glass,  it  ought  to  show  a  fairly  uniform 
field  if  examined  with  a  one-sixth  objective,  using  polarized 
light  and  a  selenite  plate.  Other  fats  melted  and  cooled,  and 
mixed  with  butter,  generally  show  a  crystalline  structure  and 
a  variegated  color  with  the  selenite  plate. 

For  a  further  discussion  of  this  point  the  student  is  referred 
to  Bulletin  13,    U.    S.   Dept.  Agric,  Part  I,  pp.   29-40;    Part 

IV,  pp.  449-455. 

Specific  Gravity. — This  is  most  conveniently  determined 
at  100°  C.  by  means  of  the  Westphal  balance  (see  Allen,  The 
Analyst,  11,  223;  also  Bull.  13,  Part  IV,  pp.  430-431).  The 
pyknometer  method  is,  however,  the  one  adopted  by  the  Asso- 
ciation of  Official  Agricultural  Chemists  as  the  official  method. 
See  Bulletin  107,  p.  130. 

Melting  Point. — This  may  be  determined  by  the  capillary- 
tube  method  as  generally  employed  for  organic  substances  and 
described  in  text  books  on  organic  analysis.  (See  for  instance, 
Mulliken:  Identification  of  Pure  Organic  Compounds,  Vol.  I, 
p.  218.)  Wiley's  method,  however,  which  is  the  official  method 
of  the  A.  O.  A.  C,  has  the  advantage  that  it  avoids  the  incorrect 
results  which  are  sometimes  obtained  with  other  methods  due 
to  the  adherence  of  the  melting  fat  to  solid  surfaces.  A  descrip- 
tion of  the  method  will  be  found  in  Bull.  107,  p.  133. 

Refractive  Index. — The  determination  of  the  refractive  index 
is  especially  valuable  in  food  analysis  on  account  of  the  ease 


202 


AIR,    WATER,    AND    FOOD 


and  rapidity  with  which  the  determination  can  be  made  and 
the  fact  that  so  httle  of  the  substance  is  necessary  for  the 
determination.  Various  forms  of  refractometers  are  used  for 
the  purpose,  a  fairly  complete  description  of  which  will  be  found 


Fig.  14. 

in  some  of  the  larger  works,  such  as  Leach:  Food  Inspection 
and  Analysis,  or  Vaubel:  Quantitative  Bestimmung  organischer 
Verbindungen.  The  instrument  having  the  widest  range  is 
the  Abbe  refractometer,  in  which  the  index  of  refraction  is 
determined  by  measuring  the  total  reflection  produced  by  a 
very  thin  layer  of  the  melted  fat,  placed  between  two  prisms 


food:  analytical  methods:  butter.  203 

of  flint  glass.  This  instrument,  fitted  with  water- jacketed 
prisms  is  shown  in  Fig.  14. 

Directions. — Revolve  the  whole  instrument  on  the  axis  h  until 
it  reaches  the  stop  provided,  then  open  the  prism  casing  AB  hy 
giving  the  pin  v  a  half-turn  (to  the  right).  Be  sure  the  prism 
surfaces  are  clean.  It  not,  clean  them  carefully  with  a  soft 
cloth  and  a  little  alcohol.  Place  a  few  drops  of  the  melted 
sample  directly  on  the  surface  of  the  prism  and  clamp  the  two 
together  again  by  turning  the  pin  v  in  the  opposite  direction. 
Now  turn  the  instrument  back  (toward  the  observer)  as  far  as 
possible  and  bring  the  "  critical  line  "  into  the  field  of  vision 
of  the  telescope.  This  is  done  by  holding  the  sector  5  firmly 
with  the  hand  and  revolving  the  double  prism  by  means  of  the 
alidade  /  until  the  field  is  divided  into  a  light  ana  a  dark 
portion.  If  the  line  is  not  sharp  focus  the  ocular  ot  the  tele- 
scope. If  it  is  colored  it  is  due  to  dispersion  of  the  light  by 
the  liquid  and  should  be  corrected  by  revolving  tne  compen- 
sator T  by  the  milled  screw  M .  The  correction  is  made  by  a 
system  of  two  revolving  Amici  prisms  in  the  lower  part  of  the 
telescope.  Adjust  the  critical  line  so  that  it  falls  on  the  inter- 
section of  the  cross  hairs  of  the  telescope.  Observe  the  temper- 
ature by  the  thermometer  inserted  in  the  prism  casing.  In  the 
case  of  solid  fats  a  sufficiently  high  temperature  should  be 
maintained  by  a  current  of  warm  water  to  keep  the  sample 
well  above  its  melting  point.  A  temperature  of  30-40°  C.  is 
usually  sufficient.  Do  not  let  the  temperature  rise  above  70° 
or  the  prisms  may  be  injured.  Read  the  index  of  refraction 
directly  through  the  small  lens  L,  estimating  the  fourth  decimal. 
Calculate  the  value  for  the  refractive  index  at  25°  C. 

Notes. — The  index  of  refraction  decreases  with  rising  tem- 
perature. With  the  common  oils  and  tats  the  change  for  each 
degree  is  very  nearly  a  constant,  amounting  to  0.000365. 
Leach  and  Lythgoe*  have  devised  a  sliding  scale  by  means  of 

*  J.  Am.  Chem.  Soc.  {1904),  1193. 


r  ;>«  •  V        ■         •     .•     ' 

204  AIR,    WATER,    AND    FOOD. 

which  the  temperature  correction  may  be  readily  made  without 
reference  to  tables. 

The  values  of  «|f  for  genuine  butter  lie  between  1.4590 
and  1.4620;  for  oleoma.rgarine  the  values  range  from  1.4650  to 
1.4700. 

The  correctness  of  the  adjustment  of  the  instrument  may 
be  tested  by  the  ''  test-plate  "  which  comes  with  it,  using 
monobromnaphthalene,  or  by  means  of  distilled  water.  The 
theoretical  value  for  the  refractive  index  of  water  at  18°  C.  is 

1.3330. 

Determination  of  Water. — Directions. — Weigh  2  grams 
of  butter  into  a  shallow  metal  dish  having  a  fiat  bottom  two 
inches  in  diameter  and  containing  a  slender  stirring-rod  two 
and  a  half  inches  long.  Heat  the  butter  in  the  oven  at  100° 
C.  for  thirty  minutes,  cool  in  a  desiccator,  and  weigh.  Heat 
again  for  periods  of  fifteen  minutes,  until  the  weight  remains 
constant  within  2  or  3  milligrams.  During  the  process  of  heat- 
ing stir  the  butter  frequently  to  hasten  evaporation  of  the  water. 

Determination   of  Ssilt.-- Directions. — Weigh     10    grams 

of  butter  in  a  small  beaker,   add  30  c.c.   of  hot  water,   and 

when   the   fat  is  completely  melted  transfer  the  whole   to  a 

separatory    funnel.     Shake    the    mixture    thoroughly,     allow 

the  fat  to  rise  to  the  top,  and  draw  off  the  water,  taking  care 

that  none  of  the  fat-globules  pass  the  stopcock.     Repeat  the 

operation  four  times,  using  30  c.c.  of  water  each  time.     Make 

the  washings  up  to  250  c.c,  mix  thoroughly,  and  titrate  25 

N 
c.c.  m  a  six-incli  porcelain  dish,  using:   —  silver  nitrate  with 

^   20 

potassium  chromate  as  an  indicator. 

Complete  Analysis  of  Butter  in  One  Sample. — Direc- 

tlons. — Weigh    about    2    grams    of   butter   into    a    platinum 

Gooch  crucible,  half-filled  with  ignited  fibrous  asbestos,  and 

dry  it  at  100°  C.  to  constant  weight.     The  loss  in  weight  is 

the  amount   of  ivatcv.     Then   treat   the   crucible   repeatedly 


UNIVERSfTY  OF  CALIFOR 

OCPARTMCNT^F  CIVIL  ENGINE 

BERKC^CY,  CAUFORNI. 


A.    Butter  X  30- 

C.   Oleomargarine  X  30- 


B.   Beef-fat  X  30 
D.    Lard  X  30- 


food:     ANALYTIC:AL    METiKJDS:    HITTTER.  205 

with  small  porti(jns  of  petroleum  ether,  iisinj^  gentle  suction, 
and  again  dry  it  to  constant  weight.  The  difference  between 
this  and  the  preceding  weight  will  hj  the  amount  of  fat. 
Now  carefully  heat  the  ci'ucihle  over  a  s'ra'l  tlame  ov  in  a 
mufTle  until  a  light  grayish  ash  is  obtained.  The  loss  in 
weight  is  the  amount  of  curd,  and  the  residual  increase  in 
\\ei<»ht  over  that  of  the  crucible  and  asbestos  is  the  (7.s7/.  If  de- 
sired, the  salt  may  be  washed  out  of  the  ash  anrl  deiermined 
by  titration  with  siKer  nitrate  after  ncutrahziiig  the  solution 
with  calcium  carljonate. 

FLOUR,  PREPARED  CEREALS,  ETC. 

This  class  of  foodstuffs  is  usually  in  a  dry  form  and  not 
liable  to  rapid  change  by  micro-organisms,  and  the  examina- 
tion consists  in  the  determination  of  their  ''  food  value."  This 
may  require  a  simple  analytical  process,  as  in  the  case  of  the 
(piantity  of  nitrogen  in  a  sample  of  ''gluten  "  sold  for  diabetic 
patients,  or  in  the  case  of  a  brand  of  flour  to  be  used  in  a 
hospital  or  State  institution.  It  may  also  require  an  estimation 
of  the  available  food-material,  as  in  the  case  of  two  kinds  of 
beans  or  corn.  The  results  of  chemical  analysis  will  often  put 
the  statements  made  on  packages  of  breakfast  cereals  in  a 
different  light. 

Owing  to  the  extensive  use  at  present  of  various  cereal 
breakfast  foods,  many  of  which  are  modified  from  their  original 
composition  by  cooking  or  treatment  with  malt,  the  extent  to 
which  the  starch  has  by  this  treatment  been  converted  to 
soluble  forms  is  also  an  important  question  for  consideration. 
The  actual  determination  of  digestibility  belongs  to  physio- 
logical chemistry  and  need  not  be  taken  into  consideration  here. 

Moisture. — Directions. — Spread  about  2  grams  of  the  fmely 
ground  material  in  a  thin  layer  on  a  watch-glass  and  dry  it 
in  the  oven  at  100°  C.  for  five  hours.     On  account  of  the  ready 


2o6  AIR,    WATER,    AND    FOOD. 

absorption  of  moisture  by  the  dried  sample,  the  use  of  cUpped 
watch-glasses  will  be  found  advantageous. 

Note. — With  some  substances  drying  in  a  current  of  hydrogen 
or  some  inert  gas  may  be  necessary,  but  for  most  cereals  the 
method  given  will  be  found  satisfactory. 

Ash. — Directions.— \\iQ\g\i  about  2  grams  into  a  platinum 
dish,  such  as  is  used  for  the  determination  of  solids  in  milk, 
and  char  it  carefully.  Ignite  at  a  very  low  red  heat  until  the 
ash  is  white,  preferably  in  a  muffle. 

Notes. — If  a  white  ash  cannot  be  obtained  in  this  manner, 
exhaust  the  charred  mass  with  water,  collect  the  insoluble 
residue  on  a  filter,  burn  it,  add  this  ash  to  the  residue  from 
the  evaporation  of  the  aqueous  extract  and  heat  the  whole  at 
a  low  red  heat  until  the  ash  is  white. 

Some  cereals,  such  as  whole  wheat  and  barley,  will  act 
destructively  on  platinum  dishes,  on  account  of  the  phosphates 
present  but  can  be  ignited  safely  in  platinum  in  the  muffle. 

Ether  Extracts:  Fats  and  Oils. — Directions. — Place  the 
residue  from  the  determination  of  moisture,  as  described  above, 
in  an  extraction-cone  and  extract  it  with  pure  anhydrous 
ether  for  sixteen  hours.  Evaporate  off  the  ether  and  dry  the 
residual  fat  at  the  temperature  of  boiling  water  to  constant 
weight. 

The  ether  extract  of  cereals  is  not  pure  fat  but  may  contain 
more  or  less  coloring  matter  or  resins.  Petroleum  ether  can  be 
used  for  the  extraction,  giving  results  not  essentially  different 
from  those  obtained  with  anhydrous  ethyl  ether. 

Total  Proteids:  Determination  of  Nitrogen  by  the 
Kjeldahl  Process.* — Principle. — Oxidation  of  carbon  and 
hydrogen,  and  conversion  of  organic  nitrogen  to  ammonium 
sulphate  by  means  of  boiling  sulphuric   acid  in  presence  of 

.  *  Ztschr.  anal.  Cheni.,  22  {188^),  366. 


food:  analytical  methods:  butter.  207 

mercury,  the  latter  acting  as  a  carrier  of  oxygen,  and  being 
converted  to  mercuric  sulphate.  Precipitation  of  mercury  by 
potassium  sulphide  to  prevent  the  formation  of  mercur-ammo- 
nium  compounds  when  the  solution  is  made  alkaline.  Setting 
f^ee  of  ammonia  by  neutralization  of  the  acid  by  potassium 
hydroxide.     Distillation  of  ammonia  into  a  measured  quantity 

of  ^—  acid.     Titration  of  excess  of  acid. 
10 

Directions. — Transfer  about  0.5  gram  of  the  finely  divided 
substance  from  a  weighing-tube  to  a  pear-shaped  digestion 
flask,  add  10  c.c.  of  concentrated  sulphuric  acid  free  from 
nitrogen,  and  0.2  gram  (three  small  drops)  of  metalHc  mercury. 
Place  a  small  funnel  in  the  neck  of  the  flask,  which  should  be 
supported  in  an  inclined  position  on  wire  gauze  and  heated 
with  a  small  flame  until  frothing  has  ceased  and  the  liquid  boils 
quietly.  Then  increase  the  heat  and  boil  the  solution  for  at 
least  half  an  hour  after  it  becomes  colorless.  Allow  the  flask 
to  cool  for  a  minute  or  two,  and  add  a  few  crystals  of  potassium 
permanganate  until  the  liquid  has  acquired  a  slight  green  or 
purple  color. 

N 
Measure  25  c.c.  of  —  acid  from  a  burette  into  a  ^00-c.c. 
10  ^ 

Erlenmeyer  flask  and  place  the  condenser- tip  beneath  the 
surface  of  the  liquid,  adding  a  little  water,  if  necessary,  to 
seal  it. 

Transfer  the  digestate  with  several  small  portions  of  distilled 
water  to  the  distilling  flask  of  the  apparatus,  add  20  c.c.  of 
potassium  sulphide  solution,  and  connect  the  flask  with  the 
condenser.  Add  50  c.c.  of  caustic  potash  through  the  separa- 
tory  funnel,  and  distil  off  the  ammonia  by  steam.  When  200 
c.c.  have  distilled  over,  remove  the  collecting-flask,  after  rinsing 
off  the  condenser-tip  with  distilled  water,  and  titrate  the  excess 

N 
of  acid  with  —  sodium  hydroxide,  using  methyl  orange  or 


2o8  AIR,    WATER,    AND     FOOD. 

cochineal  as  indicator.  If  using  new  reagents,  a  blank  deter- 
mination should  be  made  with  0.5  gram  of  cane-sugar  in  order 
to  reduce  any  nitrates  present  which  might  otherwise  escape 
detection. 

Notes. — The  temperature  during  the  digestion  must  be 
maintained  at  or  near  the  boiling-point  of  the  acid,  since  at  a 
lower  temperature  the  formation  of  ammonia  is  incomplete. 

The  process  is  considered  by  Dafert  *  to  take  place  in  four 
steps:  (i)  the  sulphuric  acid  takes  the  elements  of  water  from 
the  organic  matter;  (2)  the  sulphur  dioxide  produced  by  the 
action  of  the  residual  carbon  on  the  sulphuric  acid  exercises 
a  reducing  action  on  the  nitrogenous  bodies;  (3)  the  nitro- 
genous substances  formed  in  this  way  are  converted  to  am- 
monia by  a  process  of  oxidation;  (4)  the  ammonia  formed  is 
fixed  by  the  acid  as  ammonium  sulphate. 

In  some  cases  the  potassium  permanganate  is  necessary 
to  insure  the  complete  conversion  of  the  nitrogenous  bodies 
into  ammonia,  although  it  is  probable  that  its  use  is  unneces- 
sary in  the  majority  of  analyses. 

The  Kjeldahl  process  in  the  form  outlined  above  is  not 
applicable  to  the  determination  of  nitrogen  in  the  form  of 
nitrates.  In  order  to  render  it  of  more  general  application 
various  modifications  of  the  method  have  been  proposed,  the 
one  generally  used  in  this  country  being  that  suggested  by 
Scovell.t  In  this  method  salicylic  acid  is  used  with  the  sul- 
phuric acid,  being  converted  by  the  nitrate  into  nitro-phenol. 
By  the  use  of  sodium  thiosu'phate  or  zinc-dust  this  is  reduced 
to  amido-phenol.  The  amido-phenol  is  transformed  into  am- 
monium sulphate  by  the  heating  with  sulphuric  acid,  the  use 
of  mercury  being  absolutely  necessary  in  this  case  to  secure 


*  Ztschr.  anal.  Chem.,  24  (188^),  455. 
t  U.  S.  Dept.  Agr.,  Bull.  16  {1887),  51. 


food:  analytical  methods:  cereals.  209 

the  complete  transformation.  It  is  true  also  that  certain  other 
nitrogenous  bodies,  notably  the  alkaloids  and  certain  organic 
bases,  do  not  yield  all  their  nitrogen  to  the  Kjeldahl  process 
without  modifications  which  complicate  the  method.  For  a 
discussion  of  the  efficiency  of  these  various  modifications  the 
student  is  referred  to  a  paper  by  Sherman  and  Falk.* 

The  per  cent,  of  proteids  may  be  found  by  multiplying  the 
per  cent,  of  nitrogen  by  an  appropriate  factor,  the  one  in  general 
use  being  6.25.  Recent  work  has  shown,  however,  that  most 
of  the  proteids  of  cereals  contain  more  than  16  per  cent,  of 
nitrogen,  so  that  the  factor  6.25  gives  results  that  are  too  high. 
Because  all  the  older  w^ork  was  calculated  on  this  factor,  it  is 
still  generally  used,  nevertheless. 

Kjeldahl-Gunning  Method. — The  Gunning  method  can  be 
used  in  all  cases  where  the  Kjeldahl-Wilfarth  modification,  just 
described,  is  employed,  and  in  some  ways  it  is  simpler. 

The  digestion  and  distillation  are  carried  out  as  described 
on  page  207,  using  the  same  amount  of  sample,  together  with 
20  c.c.  of  concentrated  sulphuric  acid  and  10  grams  of  powdered 
potassium  sulphate.  No  mercury  and  consequently  no  potas- 
sium sulphide  is  used.  100  c.c.  of  the  potash  should  be  added 
instead  of  50. 

Note. — The  potassium  sulphate  is  added  to  raise  the  boiling 
point  of  the  sulphuric  acid  and  thus  shorten  the  time  required 
for  the  digestion. 

Carbohydrates. — The  total  carbohydrates,  often  stated  in 
analyses  as  "  nitrogen-free  extract,"  may  be  readily  obtained 
by  subtracting  from  100  the  sum  of  the  percentages 
of  the  other  constituents,  viz.,  moisture,  ash,  ether  extract, 
and  nitrogenous  bodies.  In  many  cases,  however,  espe- 
cially with    the    cooked   or    treated    cereals    and    with   such 

*  J.  Am.  Chem.  Soc.  {1904),  26,  1469. 


2IO  AIR,    WATER,    AND    FOOD. 

classes  of  cereal  preparations  as  infant  or  invalid  foods,  a 
further  study  of  the  carbohydrates  is  desirable.  These  are 
made  up  of  two  general  classes:  (a)  soluble  carbohydrates, 
including  sugars,  as  sucrose,  dextrose  and  maltose,  dextrin 
and  soluble  starch,  by  the  latter  term  being  meant  starch 
which  is  soluble  in  water  but  still  gives  the  characteristic 
blue  color  with  iodine,  in  distinction  from  some  of  the  more 
completely  broken-down  forms  like  dextrin,  which  no 
longer  give  blue  or  purple  colors  with  iodine;  {b)  insoluble 
carbohydrates,  including  starch,  pentosans,  lignin  bodies,  and 
cellulose.  The  three  latter  occur  chiefly  in  the  husk  or 
envelope  of  the  grain  or  in  the  w^oody  fibre  of  the  plant. 
The  pentosans  or  gums  are  distinguished  from  one  another 
by  the  formation  of  specific  sugars  upon  hydrolysis  with 
acids.  For  ordinary  analytical  purposes  it  is  sufficient  to 
determine  the  lignin  and  cellulose  together  as  "  crude  fibre." 
Since  the  exact  procedure  to  be  followed  in  the  determina- 
tion of  the  carbohydrates  varies  largely  with  each  specific 
case,  only  a  general  outline  can  be  presented  here. 

Sugars. — The  finely  ground  material,  previously  dried 
and  extracted  with  ether  for  the  removal  of  crude  fat,  is 
extracted  with  85  per  cent,  alcohol.  In  the  extract  the 
reducing  sugars  may  be  determined  by  means  of  Fehling's 
solution  as  described  on  page  181,  and  the  sucrose  deter- 
mined in  the  same  way  after  inversion  wdth  hydrochloric 
acid. 

Dextrin  and  Soluble  Starch. — The  residue  from  the  ex- 
traction of  the  sugars  is  treated  for  eighteen  to  twenty-four 
hours  with  water  at  laboratory  temperature  with  frequent 
agitation,  made  up  to  definite  volume,  and  filtered.  This 
may  be  tested  with  iodine,  and  if  no  blue  color  is  produced, 
evaporated  to  small  volume,  and  the  dextrin  converted  to 
dextrose  by  dilute  hydrochloric  acid  and  determined  by 


food:  analytical  methods:  cereals.  211 

Fchling's  solution.  In  some  few  cases,  however,  a  blue 
color  with  iodine  may  indicate  the  presence  of  soluble  starch, 
in  which  case  an  aliquot  part  of  the  filtrate  n_ay  be  treated 
with  an  excess  of  barium  hydroxide  to  precipitate  the  starch. 
In  the  filtrate  from  this  precipitate  the  dextrin  is  deter- 
mined by  inversion  and  copper  reduction  as  before.  The 
difference  between  the  dextrin  thus  found  and  the  first 
determination  gives  the  soluble  starch. 

Starch. — The  methods  for  the  determination  of  starch 
vary  with  the  condition  in  which  the  starch  is  found.  In  the 
case  of  nearly  pure  starch  it  may  be  converted  into  dextrose 
by  boiling  with  dilute  acid,  the  dextrose  being  then  deter- 
mined by  Fehling's  solution  in  the  usual  way.  Hot  acids, 
however,  cannot  be  used  to  convert  starch  in  the  natural 
state,  as  it  is  found  in  cereals,  because  other  carbohydrate 
bodies,  especially  the  pentosans,  become  soluble  under  these 
conditions  and  the  results  are  too  high.  In  such  cases  the 
starch  is  brought  into  solution  by  treatment  with  diastase  or 
by  heating  with  water  under  pressure.  The  results  obtained 
by  direct  acid  hydrolysis,  however,  in  cases  where  the  highest 
accuracy  is  not  required,  may  be  sufficient  and  the  method  is 
much  quicker  and  easier  of  execution  than  the  digestion  with 
diastase. 

Direct  Acid  Hydrolysis. — Directions. — Weigh  out  from  2 
to  5  grams  of  the  sample,  depending  upon  the  amount  of  starch 
present,  and  wash  on  a  filter  with  five  successive  portions  of 
10  c.c.  each  of  ether.  Allow  the  ether  to  evaporate  from  the 
residue  and  then  wash  it  with  10  per  cent,  alcohol  until  free 
from  soluble  carbohydrates.  150  c.c.  of  the  dilute  alcohol  is 
generally  sufficient,  but  if  much  reducing  sugar  or  dextrin  is 
present,  as  may  be  the  case  with  malted  cereals,  more  will  be 
necessary.  Wash  the  residue  from  the  filter  with  200  c.c.  of 
water  into  a  500  c.c.  graduated  flask,  add  20  c.c.  of  hydrochloric 
acid,  sp.  gr.  1.125,  place  a  funnel  in  the  neck  of  the  flask  to 


212  AIR,  WATER,    AND    FOOD. 

retard  evaporation,  and  heat  in  a  boiling  water  bath  for  two  and 
one-half  hours.  Cool,  nearly  neutralize  with  sodium  hydroxide 
and  make  up  to  500  c.c.  Filter,  and  determine  dextrose  in  an 
aliquot  portion,  25  or  50  c.c.,  of  the  filtrate,  using  the  method 
described  on  page  181.  Convert  dextrose  to  starch  by  the 
factor  0.9. 

Note. — The  washing  to  remove  soluble  carbohydrates  is 
performed  with  dilute  alcohol  rather  than  with  water  because 
the  fonner  is  less  likely  to  carry  starch  granules  through  the 
paper.  The  sugar  solution  when  added  to  the  Fehling's  solution 
should  be  clear  and  only  faintly  acid.  It  should  in  general 
contain  not  m^ore  than  0.5  per  cent,  of  reducing  sugar. 

Determina.tion  with  Diastase. — Directions. — Treat  2  to  5 
grams  of  the  sample  with  ether  and  dilute  alcohol,  as  in  the 
previous  method,  and  wash  the  residue  into  a  250-c.c.  flask 
with  50  c.c.  of  water.  Heat  slowly  to  boiling,  or  immerse  the 
flask  in  boiling  water,  until  the  starch  gelatinizes,  stirring 
constantly  to  prevent  the  formation  of  lumps.  Cool  to  55°  C, 
add  20-40  c.c.  of  malt  extract,  and  keep  the  solution  within 
tw^o  degrees  of  the  stated  temperature  for  an  hour  or  until  the 
solution  no  longer  gi\'es  the  starch  reaction  with  iodine  under 
the  microscope.  In  either  case  heat  the  solution  again  to 
boiling  to  gelatinize  any  remaining  starch  granules,  test  again 
and  if  starch  is  found,  cool  to  55°  C,  and  treat  as  before,  using 
a  fresh  portion  of  malt  extract.  Continue  this  treatment  until, 
when  carefuUy  examined  under  the  microscope,  a  drop  of  the 
solution  fails  to  give  the  iodine  reaction  for  starch.  Cool, 
make  up  to  250  c.c.  and  filter  through  a  dry  filter.  Transfer 
200  c.c.  of  the  filtrate  to  a  500-c.c.  graduated  flask,  add  20  c.c. 
of  hydrochloric  acid,  sp.  gr.  1.125,  and  carry  out  the  determina- 
tion as  described  in  the  preceding  method. 

A  blank  determination  must  be  carried  through,  using  50 
c.c.  of  water  and  exactly  the  same  amount  of  malt  extract  as 


food:  analytical  methods:  cereals.  213 

iised  in  the  regular  procedure,  in  order  to  correct  for  the  cupric 
reducing  power  of  the  malt  extract. 

Malt  Extract. — Treat  40  grams  of  fresh  coarsely  ground  malt 
several  hours  with  200  ex.  of  water,  shaking  occasionally. 
Filter  and  add  a  few  drops  of  chloroform  to  prevent  the  growth 
of  molds. 

Notes. — The  action  of  the  diastase  on  the  gelatinized  starch 
is  to  convert  it  into  maltose  and  dextrin,  that  is,  into  soluble 
bodies  that  can  be  separated  by  filtration  from  the  pentosans 
and  other  carbohydrates  that  give  the  high  results  in  the  direct 
acid  method.  By  the  action  of  acid  (hydrolysis)  the  maltose 
and  dextrin  are  converted  to  dextrose. 

The  determination  should,  if  possible,  be  carried  through 
without  interruption.  In  case  this  cannot  be  done  salicylic 
acid  may  be  used  to  prevent  fermentation,  not  adding  it,  how- 
ever, until  after  the  digestion  with  diastase. 

If  the  malt  itself  is  not  readily  procurable,  certain  forms 
of  prepared  diastase  are  on  the  market  and  may  be  found  more 
convenient  either  for  analytical  use  or  for  purposes  of  illustra- 
tion. When  possible,  however,  it  is  preferable  to  use  the  freshly 
prepared  malt  extract,  as  the  prepared  diastase,  made  at 
different  times  and  from  separate  portions  of  malt,  may  show 
great  differences  in  hydrolytic  power. 

It  is  sometimes  convenient  to  use  freshly  collected  saliva, 
this  being  free  from  carbohydrate.  In  this  case  the  digestion 
should  be  carried  out  at  38°  C.  instead  of  55°  C. 

Pentosans. — These  are  determined  usually  directly  upon 
the  original  material.  The  methods  in  general  use  depend 
upon  the  conversion  of  the  pentose  substance  into  furfural 
by  distillation  with  strong  acid  and  the  subsequent  precipi- 
tation and  estimation  of  the  furfural.  The  latter  may  be  done 
by  treatment  with  phenylhydrazine  acetate  and  formation  of 
the  furfural  hydrazone,  or  by  the  formation  of  an  insoluble 


214  AIR,    WATER,    AND    FOOD. 

condensation  product  with  phloroglucin  according  to  the  method 
of  Councler. 

For  the  details  of  these  methods  reference  may  be  made 
to  Wiley,  "  Principles  and  Practice  of  Agricultural  Analysis," 
Vol.  Ill,  p.  178  et  seq.,  also  an  article  by  Shennan.*  The 
phloroglucin  method  is  given  as  a  provisional  method  in  Bull. 
107  of  the  Bureau  of  Chemistry. 

Crude  Fibre. — The  Weende  method,  the  method  adopted 
by  the  Association  of  Ofhcial  Agricultural  Chemists,  is  based 
on  the  assumption  that  the  starch  and  other  digestible  carbo- 
hydrates and  proteid  will  be  rem.oved  from  the  cereal  by  succes- 
sive digestion  at  a  boiling  tem.perature  with  acid  and  alkali  of 
a  definite  strength.  The  complex  body  thus  obtained  is  not  a 
definite  chemical  compound,  but  may  be  considered  as  being 
composed  largely  of  cellulose. 

Use  2  grams  of  the  finely  ground  sample  and  wash  on  a 
filter  with  5  portions  of  10  c.c.  each  -of  ether.  (The  residue 
from  the  determination  of  "  ether  extract  "  can  be  used  if 
desired. ) 

Transfer  the  washed  material  to  a  500-c.c.  Erlenmeyer  flask, 
add  200  c.c.  of  boiling  1.25  per  cent,  sulphuric  acid,  place  a 
funnel  in  the  neck  of  the  flask  and  boil  gently  for  30  minutes. 
Filter  on  a  ribbed  filter  and  wash  with  several  portions  of  boiling 
water.  Transfer  the  precipitate  by  means  of  200  c.c.  of  boiling 
1.25  per  cent,  sodium  hydroxide  in  a  small  wash-bottle  to  the 
same  500-c.c.  Erlenm.eyer  flask,  and  boil  again  gently  for  30 
minutes. 

Filter  on  ignited  asbestos  in  a  Gooch  crucible,  wash  with 
boiling  water  until  free  from  alkali,  then  with  10  c.c.  of  alcohol, 
and  finally  with  10  c.c.  of  ether.  Dry  at  the  temperature  of 
boiling  water   to   constant   weight.     Ignite   carefuUy   at   first, 

* /.  Am.  Chem.  Soc,  19  {i8gj),  291. 


food:  analytical  methods:  cereals.  215 

then  at  a  low  red  heat  until  the  organic  matter  is  destroyed. 
Calculate  the  loss  on  ignition  as  "  crude  fibre." 

Note. — The  filtration  will  be  found  to  proceed  fairly  rapidly 
if  the  solution  is  filtered  hot  and  care  is  taken  to  keep  the 
residue  from  the  filter  as  long  as  possible. 

The  sulphuric  acid  and  sodium  hydroxide  should  be  carefully 
prepared  and  the  strength  determined  by  titration. 

EXAMINATION    OF   FERMENTED    LIQUORS. 

WINE. 

General  Statements. — The  object  of  a  wine  analysis  is 
ordinarily  to  determine  whether  or  not  a  wine  is  pure  and 
unadulterated,  or  whether  it  has  been  properly  made. 
Special  works  furnish  sufficient  information  concerning  pro- 
cesses of  manufacture,  and  it  is  essential  to  know  here  only 
the  general  composition  of  the  grape- juice  or  "must"  and 
how,  by  the  natural  process  of  fermentation,  this  may  be 
altered  in  the  finished  product. 

The  "  must  "  contains  sugars  (mainly  dextrose) ;  dextrin ;, 
organic  acids  and  salts,  mainly  tartaric  and  malic  acids; 
salts  of  inorganic  acids,  chiefly  phosphates,  sulphates,  and 
chlorides.  Various  extractive  matters,  which  largely  affect 
the  color  and  flavor  of  the  wine,  together  with  a  little  tannin 
and  albuminous  substances,  are  also  present.  The  wine  will 
contain  then,  besides  water,  the  following :  Alcohol,  glycerine, 
frequently  some  sugar  that  has  escaped  fermentation,  ethers, 
which  determine  largely  the  ''bouquet"  of  the  wine,  and 
more  or  less  of  the  acids,  salts,  coloring  and  extractive  mat- 
ters of  the  must,  together  with  varying  amounts  of  carbonic, 
acetic,  and  succinic  acids. 

According  to  differences  in  their  composition  wines  may 
be  divided  into  various  classes,  such  as  "  dry  "  wines,  which 


2l6  AIR,    WATER,    AND    FOOD. 

contain  very  little  sugar,  as  distinguished  from  the  sweet 
wdnes,  in  which  a  notable  quantity  of  sugar  has  escaped 
fermentation,  or  to  which  an  addition  of  sugar  has  been 
made  subsequent  to  the  main  fermentation.  Or  they  may 
be  divided  according  to  the  content  of  alcohol  into  natural 
wines  and  those  fortified  by  addition  of  alcohol,  as  port, 
sherry,  and  madeira. 

The  composition  of  the  wine  may  be  changed,  moreover, 
by  the  various  methods  which  are  used  for  its  "improve- 
ment," such  as  fortification  already  mentioned,  plastering, 
petiotization,  etc.  Information  regarding  these  methods 
^N\\\  be  found  in  some  of  the  larger  works  mentioned  in  the 
bibliography. 

The  determinations  of  most  value  in  judging  the  purity 
of  wine  are  alcohol,  glycerine,  extract,  ash,  total  and  volatile 
acids.  The  actual  percentages  of  these  substances  are  not  of 
so  great  value  as  certain  relations  betw^een  them,  such  as 
the  ratio  of  ash  to  extract,  extract  to  alcohol,  alcohol  to 
glycerine,  alcohol  to  acids,  and  volatile  to  total  acids. 
Examination  for  preservatives  and  foreign  coloring  matters 
should  also  be  made.  It  should  be  remembered,  however, 
in  judging  the  quality  of  American  whines  that  the  standards 
of  European  practice  are  not  entirely  applicable  and  that 
further  study  will  be  necessary  before  even  tentative  stand- 
ards can  be  fixed. 

Specific  Gravity. — This  is  to  be  taken  by  means  of  the 
Westphal  balance  or  Sprengel  tube  at  15°. 5  C. 

Notes. — Where  the  specific  gravity  of  the  sample  is  known, 
the  various  portions  taken  for  analysis  can  be  more  conven- 
iently measured  than  weighed.  The  results  can  be  calculated 
to  per  cent,  by  weight  by  dividing  the  results  expressed  as 
^rams  per  100  c.c.  by  the  specific  gravity. 

Efferv^escing  wines  should,   before   analysis,   be   vigorously 


food:  analytical  methods:  fermented  liquors.      217 

shaken  in  a  large  flask  to  hasten  the  escape  of  carbon  dioxide. 
The  hquid  may  then  be  poured  from  under  the  foam  into 
another  vessel. 

Alcohol. — Principle. — The  alcohol  is  obtained  freed  from 
everything  but  water,  and  its  amount  determined  by  ascertain- 
ing the  specific  gravity  of  the  mixture,  and  taking  the  per  cent, 
from  the  tables. 

Directions. — Measure  (or  weigh)  100  c.c.  of  the  wine  into 
a  500-C.C.  round-bottomed  flask.     Add  50  c.c.  of  water,  neutralize 

N 
free  acid  with  —  sodium  hydroxide,  and  add  0.5  gram  of  tannic 

acid,  if  necessary,  to  prevent  foaming.  Distil  off  about  95  to 
98  c.c.  into  a  loo-c.c.  graduated  flask.  Fill  up  to  the  mark 
with  distilled  water,  mix  thoroughly,  and  take  the  specific 
gravity  of  the  distillate  at  i5°.5  C.  with  a  pyknometer.  The 
percentage  of  absolute  alcohol  by  volume  corresponding  to 
the  observed  density  will  be  found  in  Table  X,  page  244. 

To  find  the  alcohol  by  weight  in  the  sample,  multiply  the 
per  cent,  of  alcohol  in  the  distillate  as  taken  from  the  table,  by 
the  weight  of  the  distillate  and  divide  the  result  by  the  weight 
of  the  sample  used. 

Notes. — The  object  of  neutralizing  the  wine  with  sodium 
hydroxide  is  to  prevent  the  distillation  of  volatile  acids,  prin- 
cipally acetic.  A  certain  amount  of  volatile  ethers  may  also 
pass  over  into  the  distillate,  but  in  most  cases  it  is  so  slight 
that  its  influence  may  be  neglected. 

Normal  wines  ordinarily  contain  between  4.5  and  12  per 
cent,  of  alcohol  except  in  the  case  of  "  fortified  "  wines,  where 
the  amount  may  be  even  20  per  cent.  Fermentation  does 
not  yield  more  than  about  14  per  cent,  of  alcohol. 

Extract. — The  method  to  be  employed  depends  on  the 
proportion  of  extract.  A  preliminary  calculation  should  be 
made  by  the  aid  of  the  formula 


2l8  AIR,  WATER,    AND    FOOD. 

where  x  is  the  specific  gravity  of  the  dealcoholized  wine,  d 
the  specific  gravity  of  the  wine,  and  d'  the  specific  gravity 
of  the  distillate  obtained  in  the  determination  of  alcohol.  The 
value  for  x  is  found  from  Table  XI,  page  247. 

Dry  Wines. — (Having  an  extract  content  of  less  than 
3  per  cent.)  Evaporate  50  c.c.  on  the  water-bath  to  a 
sirupy  consistency  in  a  flat-bottomed  platinum  dish.  Heat 
the  residue  in  the  oven  at  100°  C.  for  two  hours  and  a  half, 
cool  in  a  desiccator  and  weigh. 

Sweet  Wines. — When  the  extract  content  is  between  3 
and  6  per  cent,  treat  25  c.c.  of  the  sample  as  described  under 
dry  wines.  When  the  amount  of  extract  exceeds  6  per  cent. 
it  is  best  to  accept  the  result  found  from  the  table  and  not 
to  determine  it  gravimetrically. 

Notes. — The  gravimetric  determination  will  be  inac- 
curate with  wines  high  in  extract  on  account  of  the  serious 
error  caused  by  drying  levulose  at  high  temperatures.  The 
figures  in  the  table  are  based  on  determinations  made  at 
75°  C.  in  vacuo. 

Wine  made  from  the  juice  of  ripe  grapes  rarely  contains 
less  than  1.5  per  cent,  of  extract  in  the  case  of  white  wines 
and  about  2.0  per  cent,  in  the  case  of  red  wines.  The 
amount  of  extract  decreases  of  course  with  age. 

Alcohol-extract  Ratio. — The  municipal  laboratory  of 
Paris  considers  a  wine  "fortified"  if  the  alcohol  exceeds  4.5 
times  the  extract  for  red  wines  and  6.5  for  white  wines.  The 
amount  of  added  alcohol  is  calculated  by  the  municipal 
laboratory  by  subtracting  the  ''natural"  alcohol  (extract 
X4.5  or  6.5)  from  the  total  alcohol. 

Ash. — Ignite  the  residue  from  the  extract  determination 
as  described  on  page  206. 

Note. — The  amount  of  ash  in  a  natural  wine  averages 
about  10  per  cent,  of  the  extract,  varying  ordinarily  be- 
tween 0.14  per  cent,  and  0.35  per  cent. 


food:  analytical  methods:  fermented  liquors.      219 

Glycerine.^ — Evaporate  100  c.c.  of  wine   in  a  porcelain 
dish  on  the  water-bath  to  a  volume  of  about  10  c.c,  and 
treat  the  residue  with  about  5  grams  of  fine  sand  and  with 
from   1.5   to   2   c.c.  of  milk  of  lime   (containing  40  grams 
Ca(0H)2  per  100  c.c.)  for  each  gram  of  extract  present,  and 
evaporate  almost  to  dryness.     [With  wines  whose  extract 
exceeds  5  grams  per  100  c.c,  heat  the  portion  to  be  used  in 
the  determination  of  glycerine  to  boiling  in  a  flask,  and 
treat  with  successive  small  portions  of  milk  of  lime  until 
it  becomes,  first,   darker,   and  then  light  in  color.     When 
cool,  add  200  c.c  of  96  per  cent,  alcohol  (sp.  gr.  0.8118), 
allow  the  precipitate  to  subside,  filter,  and  wash  with  96 
per  cent,  alcohol  (sp.  gr.  0.8118).     Evaporate  the  filtrate 
to  about  10  c.c,  add  about  5  grams  of  sand  and  from  1.5 
to    2  c.c.  of  milk  of  lime,  and   proceed  as  before.]     Treat 
the  moist  residue  with  5  c.c  of  alcohol  (96  per  cent,  by  vol- 
ume), remove  the  substance  adhering  to  the  sides  of  the 
dish  with  a  spatula,  and  rub  the  whole  mass  to  a  paste,  with 
the  addition  of  a  little  more  alcohol.     Heat  the  mixture  on 
the  water-bath,  with  constant  stirring,  to  incipient  boiling, 
and  decant  the  liquid  into  a  flask  graduated  at  100  and  no 
c.c.     W^ash   the   residue   repeatedly   by    decantation   with 
10  c.c.  portions  of  hot  96  per  cent,  alcohol.     Cool  the  con-: 
tents  of  the  flask  to  15°,  dilute  to  the  iio-c.c.  mark  with 
96   per  cent,    alcohol,    and    filter   through   a   folded   filter. 
Evaporate  100  c.c  of  the  filtrate  to  a  sirupy  consistency 
in  a  porcelain  dish,  on  a  hot,  but  not  boiling,  water-bath, 
transfer  the  residue  to  a  small  glass-stoppered  graduated 
cylinder  w4th   20  c.c.   of  absolute  alcohol,   and  add  three 
portions  of  20  c.c  each  of  absolute  ether,  with  thorough 
shaking  after  each  addition.     Let  stand  until  clear,  then 
pour  off  through  a  filter,  and  wash  the  cylinder  three  times 
or  more  with  a  mixture  of  one  part  absolute  alcohol  to  one 


2  20  AIR,    WATER.   AND    FOOD. 

and  one-half  parts  of  absolute  ether,  pouring  the  wash- 
liquor  also  through  the  filter.  Evaporate  the  filtrate  to  a 
sirupy  consistency,  dry  for  one  hour  at  the  temperature  of 
boiling  water,  weigh,  ignite,  and  w^eigh  again.  The  loss  in 
ignition  increased  by  one-tenth  gives  the  glycerine. 

Xotes. — The  ratio  of  glycerine  to  alcohol  is  of  great 
importance  in  judging  the  purity  of  a  wine.  According  to 
European  standards  in  pure  w4nes  the  glycerine-alcohol 
ratio  varies  from  between  6  and  14  parts  by  Aveight  of  the 
former  to  100  of  the  latter.  The  Httle  work  done  on 
American  wines  indicates  a  lower  ratio. 

Free    Acids:    Total  Acidity  Calculated    as    Tartaric 

N 

Acid. — Titrate  10  c.c.  of  the  wdne  with —  sodium  hydroxide. 

10 

The  end-point  is  reached  when  a  drop  of  the  liquid  placed 

upon  faintly-red  litmus  paper  produces  a  blue  spot  in  the 

middle  of  the  portion  moistened.     Calculate  the  results  as 

N 
tartaric  acid.     One  c.c.  — sodium  hydroxide  =0.0075  gram 

10 

of  tartaric  acid. 

Volatile  Acids  Calculated  as  Acetic  Acid.— Measure 
50  c.c.  of  wane  into  a  300-c.c.  flask  provided  with  a  cork 
having  two  perforations.  One  is  fitted  with  a  tube  6  mm.  in 
diameter  and  blown  out  to  a  bulb  40  mm.  in  diameter  a  short 
distance  above  the  cork ;  this  tube  is  connected  with  a  con- 
denser. The  other  perforation  carries  a  tube  reaching  nearly 
to  the  bottom  of  the  flask  and  drawn  out  to  a  small  aperture 
at  its  lower  end;  this  is  connected  wdth  a  500-c.c.  flask  con- 
taining water.  Heat  both  flasks  to  boiling ;  then  lower  the 
flame  under  that  containing  the  wine,  adjusting  the  flame  so 
that  the  volume  of  liquid  remains  constant,  and  continue  the 
distillation  by  means  of  steam  until  200  c.c.  have  gone  over. 


food:  analytical  methods:  fermented  liquors.      221 

N 
Titrate  the  distillate  with  —  sodium  hydroxide,  using  phe- 

nolphthalein    as    an   indicator.      Calculate    the    results    as 

N 
acetic    acid.     One  cc. —  sodium  hydroxide  =0.0060  gram 

10 

of  acetic  acid. 

Fixed  Acids  Calculated  as  Tartaric  Acid.  —  These 
may  be  found  by  calculating  the  volatile  acids  as  tartaric  and 
subtracting  the  result  from  the  total  tartaric  acid  found  by 
direct  titration. 

Note. — The  total  acids  in  a  wine  vary  usually  between 
0.45  per  cent,  and  1.5  per  cent.  The  acid  content  is  fre- 
quently diminished  by  aging  or  by  the  separation  of  cream  of 
tartar.  The  volatile  acid  should,  in  general,  not  be  over 
0.12  to  0.16  per  cent.,  depending  upon  the  age  of  the  wine. 
A  wine  properly  made  should  not  have  the  volatile  acid, 
estimated  as  acetic,  exceed  one-fourth  of  the  total  free  acid, 
calculated  as  tartaric. 

Coloring  Matters:  Detection  of  Coal-tar  Dyes.— Double 
Dyeing  Method  of  Sostegni  and  Carpentieri* — Fifty  cc.  of  the 
sample  are  diluted  to  100  cc.  with  water,  filtered  if  necessary, 
acidified  with  from  2  to  4  cc  of  10  per  cent,  solution  of  hydro- 
chloric acid,  and  a  piece  of  woolen  cloth  which  has  been  washed 
in  a  very  dilute  solution  of  boiling  potassium  hydroxide,  and 
then  washed  in  water,  immersed  in  it  and  boiled  for  five  to  ten 
minutes.  The  cloth  is  removed,  thoroughly  washed  in  water, 
and  boiled  with  very  dilute  hydrochloric  acid  solution.  Then 
after  washing  out  the  acid  the  color  is  dissolved  in  a  solution 
of  ammonium  hydroxide  (i  to  50).  With  some  of  the  dyes 
solution  takes  place  quite  readily,  while  with  others  it  is  neces- 
sary to  boil  some  time.  The  wool  is  taken  out,  a  slight  excess 
of  hydrochloric  acid  is  added  to  the  solution,  another  piece 

*  Ztschr.  anal.  Chem.,  35  (i8g6),  397. 


222  AIR,    WATER,   AND    FOOD. 

of  wool  is  immersed  and  again  boiled.  With  vegetable  coloring 
matter  this  second  dyeing  gives  practically  no  color,  and  there 
is  no  danger  of  mistaking  a  fruit  color  for  one  of  coal-tar  origin. 

Notes. — It  is  absolutely  necessary  that  the  second  dyeing 
should  be  made,  as  some  of  the  coal-tar  dyes  will  dye  a  dirty 
orange  in  the  first  acid  bath  which  might  be  easily  passed 
for  vegetable  color  but  on  treatment  in  alkaline  bath  and 
second  acid  bath  becomes  a  bright  pink. 

Another  advantage  in  the  second  dyeing  is  that  if  a  large 
piece  of  woolen  cloth  is  used  in  the  first  dyeing,  and  a  small 
piece  in  the  second  dyeing,  small  amounts  of  coloring  matter 
can  be  brought  out  much  more  decidedly  in  the  second 
dyeing,  where  practically  all  of  the  vegetable  coloring  matter 
has  been  excluded. 

Several  colors  which  are  not  coal-tar  dyes,  notably  archil, 
archil  derivatives,  and  sulphonated  indigo,  give  reactions  by 
this  method  and  are  liable  to  be  confused  with  coal-tar  colors. 
For  hints  as  to  the  method  for  detecting  these  reference  may 
be  made  to  Bulletin  107,  Bureau  of  Chemistry,  page  190. 

Methods  for  the  further  separation  and  identification  of 
the  artificial  colors  cannot  be  taken  up  here  for  lack  of  space. 
The  student  is  referred  to  Leach:  ''Food  Inspection  and 
Analysis,""  p.  628  et  seq.;  MuUiken:  "The  Identification  of 
Commercial  DyestuffsT  and  a  paper  by  Green,  Yeoman, 
and  Jones  on  "  The  Identification  of  Dyestuffs  on  A  nimal  Fibres.'''*' 

Preservatives. — ^The  preservatives  most  commonly  em- 
ployed in  wines  are  salicylic  and  benzoic  acids.  Sulphurous 
acid  and  sulphites  are  also  used.  For  methods  of  detecting 
other  substances  less  commonly  employed,  such  as  abrastol, 
beta-naphthol,  etc.,  reference  may  be  made  to  Bulletin  107  of 
the   Bureau   of   Chemistry.     Boric    acid   is   occasionally   used, 

*  /.  Soc.  Dyers  and  Colourists,  ipo^,  236-243. 


food:  analytical  methods:  fermented  liquors.     223 

but  since  a  small  amount  of  it  is  normally  present  in  wines, 
tests,  to  be  of  value,  should  be  quantitative. 

Salicylic  Acid. — Acidify  about  50  c.c.  of  the  wine  with 
5  c.c.  of  dilute  (1:3)  sulphuric  acid  and  extract  in  a  sepaiatory 
funnel  with  25  c.c.  of  ether.  Draw  off  the  lower  layer,  wash 
the  ether  twice  with  water,  using  10  c.c.  each  time  and  finally 
evaporate  the  ether  in  a  porcelain  dish  at  room  temperature. 
To  the  residue  in  the  dish  add  2  to  3  drops  of  ferric  alum  solu- 
tion (p.  261).  or  very  dilute  ferric  chloride.  A  deep  purple 
or  violet  color  indicates  salicylic  acid. 

yotes. — Not  more  than  50  c.c.  should  be  used  for  the  test, 
since  a  trace  of  salicylic  acid  seems  normally  present  in  some 
wines. 

The  washing  with  water  is  to  free  the  ether  from  traces  of 
sulphuric  acid  which  interferes  with  the  development  of  the 
violet  color. 

Benzoic  Acid* — Acidify  about  100  c.c.  of  wine  with  sul- 
phuric acid,  extract  with  ether,  and  evaporate  the  ethereal 
solution  as  in  the  detection  of  salicylic  acid.  Treat  the  resi- 
due with  2  or  3  c.c.  of  strong  sulphuric  acid.  Heat  till 
white  fumes  appear;  organic  matter  is  charred  and  benzoic 
acid  is  converted  into  sulpho-benzoic  acid.  A  few  crystals 
of  ammonium  nitrate  are  then  added.  This  causes  the  for- 
mation of  metadinitrobenzoic  acid.  When  cool  the  acid  is 
diluted  with  water  and  ammonia  added  in  excess,  followed 
by  a  drop  or  two  of  ammonium  sulphide.  The  nitro-compound 
becomes  converted  into  ammonium  metadiamidobenzoic  acid, 
which  possesses  a  red  color.  This  reaction  takes  place  imme- 
diately, and  is  seen  at  the  surface  of  the  liquid  without  stirring. 

Sulphurous  Acid  and  Sulphites. — See  directions  under  Beer, 
page  225. 

♦Mohler:  Bull.  Soc.  Chim.  [3],  3,  {18^0)  414. 


2  24  AIR,  WATER,  AND  FOOD. 

BEER  AND  OTHER  MALT  LIQUORS. 

Before  analysis  the  sample  must  be  thoroughly  shaken  in 
a  large  flask,  in  order  to  remove  carbon  dioxide. 

Specific  Gravity. — Taken  with  a  pyknometer  or  Sprengel 
tube  at  i5°.5  C. 

Alcohol. — Determined  as  in  the  analysis  of  wine.  It  will 
not  be  necessary  to  neutralize  the  free  acid  before  distilling. 

Extract. — Determine  the  extract  content  corresponding 
to  the  specific  gravity  of  the  dealcoholized  beer  according  to 
Table  For  this  purpose  employ  the  formula 

in  which  5^  is  the  specific  gravity  of  the  dealcoholized  beer, 
g  the  specific  gravity  of  the  beer,  and  g'  the  specific  gravity 
of  the  distillate  obtained  in  the  determination  of  alcohol. 
Instead  of  using  this  formula  the  residue  from  the  distillation  of 
alcohol  is  sometimes  diluted  to  the  original  volume,  and  its 
specific  gravity  taken.  This  is  often  impracticable  owing  to 
the  necessity  of  employing  tannic  acid  to  prevent  foaming 
in  the  distilling  flask,  and  owing  to  the  coagulation  of  ■ 
proteids    during  the  distillation. 

Note. — The  extract  of  beer  cannot  be  accurately  deter- 
mined by  evaporation  and  drying  at  the  boiling-point  of 
water  because  of  the  dehydration  of  the  maltose. 

Ash. — Evaporate  25  c.c.  to  diyness  and  determine  as  in 
the  analysis  of  wine. 

Free   Acids. — Heat    20  c.c.   to    incipient   boiling    to    expel 

carbon  dioxide  and  titrate  as  in  the  analysis  of  wine.     Fixed 

acids,  consisting  principally  of  lactic  and  succinic,  are  calcu- 

N 
lated  as  lactic  acid.     One  c.c.  of  —  sodium  hydroxide  =0.0090 

gram  of  lactic  acid. 


food:  analytical  methods:  fermented  liquors.      225, 

Reducing  Sugar. — Dilute  25  c.c.  of  the  beer,  freed  from 
carbon  dioxide,  to  100  c.c.  Determine  the  reducing  sugar  in 
25  c.c.  of  this  solution  as  directed  on  page  181,  enough  water 
being  added  to  make  the  total  volume  of  the  Fehling's  solution- 
sugar  mixture  100  c.c.  Express  the  results  in  terms  of  maltose, 
as  given  in  Table  XII. 

Preservatives. — The  preservatives  most  common^  em- 
ployed in  beer  are  benzoic  and  salicylic  acids  and  their  sodium 
salts,  sulphites  and  fluorides. 

Benzoic  and  Salicylic  Acids. — Detected  as  described  under 
Wine. 

Sulphites. — Qualitative  Test. — Use  an  apparatus  similar  to 
that  described  for  the  determination  of  volatile  acids  in  wine.  TO' 
50  c.c.  of  the  sample  add  about  a  gram  of  sodium  bicarbonate, 
20  c.c.  of  20  per  cent,  phosphoric  acid,  and  immediately  con- 
nect the  flask  with  the  condenser.  Pass  steam  through  the 
flask  until  about  20  c.c.  have  collected  in  the  distillate.  To 
the  distillate  add  bromine  water  in  slight  excess  and  boil. 
Expel  the  excess  of  bromine  and  test  for  sulphunc  acid  with 
hydrochloric  acid  and  barium  chloride  in  the  usual  manner. 

Notes. — The  method  described  does  not  distinguish  between 
free  sulphurous  acid  and  that  present  in  the  form  of  sulphites. 
The  former  can  be  distilled  without  the  addition  of  phosphoric 
acid. 

The  presence  of  sulphites  in  a  sample  should  not  be  con- 
sidered evidence  of  added  preservatives  unless  an  excessive 
amount  is  found  since  the  use  of  sulphured  malt  or  hops  may 
introduce  a  small  amount.  To  obtain  conclusive  data  a  quan- 
titative determination  of  the  amount  present  should  be  made. 
This  can  be  done  by  a  method  very  similar  to  that  used  for 
the  detection,  taking  greater  precautions  against  oxidation 
and  absorbing  the  sulphurous  acid  in  standard  iodine  solution. 
Care  should  be  taken  also  to  avoid  the  distillation  of  iodine- 


2  26  AIR,    WATER,   AND    FOOD. 

reducing  substances  other  than  sulphurous  acid.  For  a  detailed 
discussion  of  the  determination  reference  may  be  made  to 
the  following  papers:  Bureau  of  Chemistry,  Bull.  107,  p.  187; 
Gudeman:  /.  Ind.  Eng.  Chem.,  1909,  p.  81;  Woodman  and 
Gadsby:   /.  Ind.  Eng.  Chem.,  1909. 

Fluorides. — The  well-known  qualitative  test  for  fluorides  by 
etching  a  glass  plate  may  be  modified  by  the  use  of  a  suitable 
condenser  and  made  sufficiently  delicate  to  be  used  here.  It 
is  possible  also  by  suitable  regulation  of  the  temperature  to 
make  the  test  approximately  quantitative.* 

FLAVORING  EXTRACTS. 

The  work  on  alcoholic  liquids  can  be  pleasantly  varied  by 
substituting  for  it  in  some  cases  the  determination  of  alcohol 
and  other  important  components  of  the  usual  flavoring  essences, 
the  most  important  of  which  are  vanilla  and  lemon.  vSeveral 
important  types  of  food  methods,  such  as  the  determination 
of  essential  oils  and  quantitative  extraction  with  volatile 
solvents,  are  also  brought  to  the  attention  of  the  student. 

VANILLA. 

Vanilla  extract  is  a  dilute  alcoholic  tincture  of  the  vanilla 
bean,  the  fruit  of  a  climbing  plant  of  the  orchid  family.  The 
best  grades  are  made  by  allowing  the  cut  and  bruised  beans  to 
macerate  in  the  alcohol  for  several  months,  the  liquid  thus 
obtained  being  deep  brown  in  color,  with  a  delightful  perfume 
and  flavor.  Sugar  is  added  to  assist  in  the  extraction  and  to 
sweeten  the  product. 

The  cost  of  a  quart  of  the  pure  extract,  according  to  Winton,t 


♦Woodman  and  Talbot:    J.  Am.  Chem.  Soc,  1906,  1437;    1907,  1362. 
t  Conn.  Agr.  Exp.  Sta.  Report,  1901,  150. 


food:  analytical  methods:  flavoring  extracts.     227 

is  from  about  60  cents  to  82.50,  depending  chiefly  upon  the 
grade  of  beans  used. 

The  composition  of  five  pure  vanilla  extracts,  made  from 
beans  of  different  grades,  is  given  in  the  following  table,  *  the 
results  being  expressed  in  per  cent,  by  weight: 


Grade  of  Bean. 


Specific 
Gravity. 


Vanillin. 


Alcohol. 


Total 
Residue 


Cane- 
sugar. 


Mexican  (whole) 

Mexican  (cut) 

South  American  (whole) 

Bourbon  (whole) 

Tahiti  (whole) 


I. 0159 
I .0146 
I .0109 
I .0166 
I .0104 


0.125 
0.065 
0.215 
0.138 
o.  108 


37-96 
39-92 
38.58 
38.32 
38.84 


22.60 
23.10 
22.00 
23-13 
21.75 


19.90 
19.20 
19.00 
20.40 
20.00 


The  adulteration  of  vanilla  extract  consists  principally  in 
the  use  of  extract  of  Tonka  bean,  a  cheap  substitute  somewhat 
resembling  vanilla  in  its  flavor,  in  the  use  of  artificial  prepara- 
tions of  the  active  principles  of  vanilla  and  tonka,  vanillin  and 
coumarin,  and  in  the  addition  of  artificial  color,  usually  cara- 
mel. A  cheap  extract  may  be  entirely  an  artificial  mixture, 
made  of  artificial  vanillin  or  coumarin,  or  both,  in  weak  alcohol, 
colored  with  caramel.  An  occasional  adulteration  is  the  use 
oi  alkali,  such  as  potassium  bicarbonate,  to  hold  the  resin  in 
solution  and  permit  the  use  of  a  more  dilute  alcohol. 

Analytical  Methods. — Alcohol. — Measure  25  c.c.  of  the 
sample,  add  100  c.c.  of  water,  and  determine  the  alcohol  by 
volume,  as  directed  on  page  217,  omitting  the  use  of  sodium 
hydroxide  or  tannic  acid. 

Vanillin  and  Coumarin. — (Method  of  Hess  and  Prescott, 
modified  by  Winton  and  Bailey. j)  Weigh  25  grams  into  a 
200-C.C.  beaker  with  marks  showing  volumes  of  25  and  50  c.c. 
Dilute  to  the  50-c.c.  mark  and  evaporate  in  a  water-bath  to 

*  Conn.  Agr.  Exp.  Sta.  Report,  1901,  150. 

t  J.  Am.  Chem.  Soc,  1905,  719;  Bur.  of  C hem.,  Bull.  107,  156. 


228  AIR,  WATER,   AND   FOOD. 

25  ex.  at  a  temperature  in  the  bath  of  not  more  than  70°  C. 
Dilute  a  second  time  to  50  c.c.  and  evaporate  to  25  c.c.  Add 
neutral  lead  acetate  solution  drop  by  drop  until  no  more  pre- 
cipitate forms.  Stir  with  a  glass  rod  to  facilitate  fiocculation 
of  the  precipitate,  filter  through  a  moistened  filter,  and  wash 
three  times  with  hot  water,  taking  care  that  the  total  filtrate 
does  not  measure  more  than  50  c.c.  Cool  the  filtrate  and  shake 
with  20  c.c.  of  ether  in  a  separatory  funnel.  Remove  the  ether 
to  another  separatory  funnel  and  repeat  the  shaking  of  the 
aqueous  liquid  with  ether  three  times,  using  15  c.c.  each  time. 
Shake  the  combined  ether  solutions  four  or  five  times  with  2 
per  cent,  ammonium  hydroxide,  using  10  c.c.  for  the  first 
shaking  and  5  c.c.  for  each  subsequent  shaking.  Set  aside  the 
combined  ammoniacal  solutions  for  the  determination  of 
vanillin. 

Wash  the  ether  solution  into  a  weighed  dish  and  allow  the 
ether  to  evaporate  at  the  room  temperature.  Dry  in  a  desic- 
cator, and  weigh.  Stir  the  residue  for  fifteen  minutes  with 
15  c.c.  of  petroleum  ether  (boihng-point  30°  to  40°  C.)  and 
decant  the  clear  liquid  into  a  beaker.  Repeat  the  extraction 
with  petroleum  ether  two  or  three  times.  Allow  the  residue 
to  stand  in  the  air  until  apparently  dry,  completing  the  drying 
in  a  desiccator.  Weigh,  and  deduct  the  weight  from  the  weight 
of  the  residue  obtained  after  the  ether  evaporation,  thus  obtain- 
ing the  weight  of  the  coumarin. 

Allow  the  petroleum  ether  extract  to  evaporate  at  room 
temperature.  If  it  is  coumarin  it  may  be  recognized  by  the 
characteristic  odor,  resembling  that  of  "sweet  grass,"  and  by 
Leach's  test  *  as  follows :    Dissolve  the  residue  in  a  few  drops  of 

N  .     . 

hot  water,  and  add  one  or  two  drops  of  —  iodine  in  potassium 

*  Leach:  ^' Food  Inspection  and  Analysis,"  738. 


food:  analytical  methods:  flavoring  extracts.      229 

iodide.  On  stirring  with  a  rod,  a  brown  precipitate  will  form, 
which  will  gather  into  dark  green  flocks.  The  reaction  is 
especially  marked  if  carried  out  in  a  white  porcelain  crucible 
or  dish. 

Slightly  acidulate  the  ammoniacal  solution  reserv^ed  for 
vanillin  with  10  per  cent,  hydrochloric  acid.  Cool,  and  shake 
out  in  a  separatory  funnel  with  four  portions  of  ether,  as 
described  for  the  first  ether  extraction.  Evaporate  the  ether 
at  room  temperature  in  a  weighed  dish,  dry  over  sulphuric 
acid,  and  weigh  the  vanillin. 

If  the  residue  is  white  it  may  be  safely  assumed  in  the 
majority  of  cases  that  it  is  pure  vanillin.  If  dark  colored, 
however,  it  should  be  purified  as  in  the  case  of  coumarin,  and 
the  percentage  calculated  from  the  loss  in  weight. 

Notes. — The  separation  of  vanillin  and  coumarin  is  based 
on  the  differences  in  their  chemical  constitution.  Vanillin  is 
hydroxjmiethoxy benzoic  aldehyde,  while  coumarin  is  the  anhy- 
dride of  orthohydroxycinnamic  acid.  On  account  of  the 
aldehydic  nature  of  the  vanillin  the  separation  by  dilute  ammo- 
nia is  possible,  the  aldehyde  ammonia  compound  of  vanillin 
being  readily  soluble  in  water,  while  the  coumarin  remains 
whoUy  in  the  ether. 

Acetanilid  has  been  reported  in  vanillin  extracts,  being 
present  as  an  adulterant  of  the  artificial  vanillin  employed, 
but  its  use  is  rare.  If  present,  it  will  be  found  in  the  residue 
from  the  petroleum  ether  extraction  and  can  be  recognized  by 
its  melting-point,  112°  C,  and  appropriate  tests. 

Resins. — Evaporate  25  or  50  c.c.  of  the  extract  to  one-third 
its  volume  on  the  water-bath  in  order  to  remove  the  alcohol. 
Make  up  to  the  original  volume  with  hot  water.  If  no  alkali 
has  been  used  in  the  manufacture  of  the  extract,  the  resin 
should  appear  at  this  point  as  a  flocculent  brown  residue.  Add 
acetic  acid  in  slight  excess,  allow  the  evaporating-dish  to  stand 


230  AIR,    WATER,     AND    FOOD. 

in  a  warm  place  for  a  time  to  separate  the  resin  completely, 
and  filter.  Wash  the  residue  on  the  filter,  and  save  both  the 
filtrate  and  residue.  Test  the  resin  by  placing  pieces  of  the 
filter,  with  the  resin  attached,  in  a  few  cubic  centimeters  of  dilute 
caustic  potash.  The  resin  is  dissolved  with  a  deep  red  color, 
and  on  acidifying  is  again  precipitated.  Test  the  filtrate  by 
adding  to  it  a  few  drops  of  basic  lead  acetate.  A  bulky  pre- 
cipitate is  formed,  on  account  of  the  organic  acid,  gums,  etc., 
present. 

Confirm  the  resin  test  by  shaking  5  c.c.  portions  of  the 
extract  in  separate  test-tubes  with  10  c.c.  of  amyl  alcohol  and 
10  c.c.  of  ether.  With  pure  extracts  the  upper  la\^ers  will  be 
colored,  varying  from  light  yellow  to  deep  brown;  with  artificial 
extracts,  free  from  resin,  the  amyl  alcohol  and  ether  layers  will 
be  uncolored. 

Note. — While  the  artificial  vanillin,  as  sold  on  the  market 
and  used  in  the  manufacture  of  low-grade  extracts,  is  identical 
with  the  vanillin  of  the  vanilla  bean,  it  is  true  that  pure  extracts 
owe  their  value  and  flavor  to  other  ingredients  as  well  as  to  the 
vanillin  present.  Among  these  "  extractive  matters"  the  resins 
are  important  from  an  analytical  standpoint,  serving  b\'  their 
presence  or  absence  to  determine  w^hether  true  vanilla  is  present 
or  the  extract  entirely  artificial.  As  a  quick  and  ready  test, 
ser\ing  to  distinguish  artificial  extracts  from  genuine  prepara- 
tions of  the  vanilla  bean,  the  amyl  alcohol  and  ether  tests  will 
be  found  especially  useful. 

Color:  Caramel. — Caramel  is  the  color  commonly  used  in 
vanilla  extracts,  although  coal-tar  dyes  have  been  found.  The 
presence  of  dyes  is  sometimes  indicated  by  the  color  of  the 
amyl  alcohol  in  testing  for  the  resin,  they  being  in  many  cases 
soluble  in  amyl  alcohol,  but  insoluble  in  ether.  The  two  tests 
for  caramel  w^hich  in  the  author's  experience  have  proven  most 
satisfactory  are  the  lead  acetate  test  and  the  paraldehyde  test. 


food:  analytical  methods:  flavoring  extracts.     231 

Lead  Acetate  Test. — The  coloring  matter  present  in  vanilla 
extracts  is  almost  completely  removed  when  the  dealcoholized 
extract  is  treated  with  a  few  cubic  centimeters  of  basic  lead 
acetate  solution.  Wlien  caramel  is  present,  the  filtrate  and 
precipitate,  if  any,  have  the  characteristic  red-brown  color  of 
caramel. 

Paraldehyde  Test. — To  15  c.c.  of  the  extract  add  2  c.c.  of 
zinc  chloride  (5  per  cent,  solution),  and  2  c.c.  of  caustic  potash 
(2  per  cent,  solution).  Filter,  wash  the  precipitate  with  hot 
water,  and  dissolve  it  in  15  c.c.  of  acetic  acid  (10  per  cent, 
solution).  Concentrate  on  the  water-bath  to  one-half  or  one- 
third  its  volume,  neutralize  the  excess  of  acid,  and  transfer  the 
clear  solution  to  a  rather  large  test-tube.  Add  three  volumes 
of  paraldehyde  and  just  enough  alcohol  to  make  the  mixture 
homogeneous.  If  caramel  is  present  a  brown  fiocculent  pre- 
cipitate will  form  on  standing  over  night. 

Note. — The  treatment  with  zinc  hydroxide  is  to  separate 
the  caramel  from  sugar,  which  is  present  in  many  extracts, 
and  interferes  with  the  paraldehyde  test.*  The  precipitate 
obtained  with  paraldehyde  is  probably  caramel  and  not  the 
product  of  a  chemical  reaction. 

LEMON. 

Lemon  extract  is  usually  made  by  dissolving  oil  of  lemon, 
obtained  by  expression  or  distillation  from  the  rind  of  the 
lemon,  in  strong  alcohol.  The  product  is  sometimes  colored 
with  the  color  of  lemon  peel.  The  Federal  standards  f  require 
a  content  of  lemon  oil  of  at  least  5  per  cent,  by  volume.  The 
expensive  ingredient  of  the  extract  is  the  alcohol,  since  alcohol 
of  at  least  80  per  cent,  strength  by  volume  must  be  used  to 
dissolve  5  per  cent,  of  lemon  oil;  hence  in  making  cheap  extracts 

*  Woodman  and  Newhall:   Tech.  Quart.,  21,  280. 

t  U.  S.  Dept.  Agric,  Ofl&ce  of  the  Secretary,  Circ.  ig. 


-232  AIR,    WATER,    AND    FOOD. 

the  manufacturer  endeavors  to  use  a  dilute  alcohol,  even  under 
the  necessity  of  omitting  a  portion  or  all  of  the  oil  of  lemon. 

The  common  forms  of  adulteration  of  lemon  extract  are  the 
use  of  weak  alcohol  and  consequent  deficiency  of  lemon  oil, 
as  already  noted;  the  substitution  for  the  lemon  oil  of  small 
amounts  of  stronger  oils,  as  oil  of  citronella,  oil  of  lemon-grass, 
and  the  like;  the  use  of  citral,  the  odorous  principle  of  lemon 
oil,  used  for  making  the  so-called  "terpeneless  lemon  extracts;" 
and  the  coloring  of  the  extracts  by  coal-tar  colors  or  turmeric. 

Preliminary  Test. — To  a  little  of  the  extract  in  a  test-tube 
add  seven  or  eight  times  its  volume  of  water.  A  high-grade 
extract  will  show  a  heavy  cloud,  due  to  the  precipitation  of  the 
lemon  oil.  If  no  cloudiness  or  turbidity  appears  it  may  be 
safely  inferred  that  no  oil  is  present. 

Alcohol. — The  determination  of  alcohol  is  somewhat  com- 
plicated in  this  case  by  the  presence  of  the  volatile  oil  of  lemon 
which  must  be  removed  before  distilling. 

Dilute  20  c.c.  of  the  extract  to  100  c.c.  with  water,  and 
pour  the  mixture  into  a  dry  Erlenmeyer  flask  containing  5  grams 
of  light  magnesium  carbonate.  Shake  thoroughly  and  filter 
through  a  dry  filter.  Measure  50  c.c.  of  the  clear  filtrate,  add 
about  15  c.c.  of  water,  and  distil  50  c.c,  as  directed  on  page  217. 
From  the  specific  gravity  of  the  distillate  determine  the  per  cent, 
of  alcohol  by  volume,  and  this,  multiplied  by  5,  will  give  the 
percentage  in  the  original  extract. 

Note. — The  magnesia  serves  to  absorb  the  precipitated 
oil  and  prevent  it  from  passing  through  the  filter. 

Lemon  Oil. — Pipette  20  c.c.  of  the  extract  into  a  Babcock 
milk  bottle;  add  i  c.c.  dilute  hydrochloric  acid  (1:1);  then 
add  from  25  to  28  c.c.  of  water  previously  warmed  to  60°  C; 
mix  and  let  stand  in  water  at  60°  for  five  minutes;  whirl  in 
centrifuge  for  five  minutes;  fill  with  warm  water  to  bring  the 
oil  into  the  graduated  neck  of  the  flask;    repeat  whirling  for 


food:  analytical  methods:  flavoring  extracts.      233 

two  minutes;  stand  the  flask  in  water  at  60°  C.  for  a  few  minutes 
and  read  the  per  cent,  of  oil  by  volume.  If  the  determination 
is  not  made  in  duplicate  the  flask  should  be  balanced  by  another 
containing  an  equal  weight  of  water.  In  case  oil  of  lemon  is 
present  in  amounts  over  2  per  cent,  add  to  the  percentage  of 
oil  found  0.4  per  cent,  to  correct  for  the  oil  retained  in  solution. 
If  less  than  2  per  cent,  and  more  than  i  per  cent,  is  present, 
add  0.3  per  cent,  for  correction. 

Refractive  Index  of  the  Oil. — ^\Vith  a  narrow  glass  tube 
remove  a  few  drops  of  the  oil  obtained  in  the  neck  of  the  Babcock 
flask  in  the  previous  determination  and  determine  its  index 
of  refraction  at  25°,  using  the  Abbe  refractometer.  The  read- 
ing for  pure  lemon  oil  at  25°  is  i. 471 5-1. 4740.  Most  of  the 
adulterants  give  a  higher  refractive  index;  oil  of  turpentine 
is  distinctly  lower. 

Color. — Test  for  coal-tar  colors  by  e^^aporating  a  portion  of 
the  extract  to  dryness  on  the  water-bath.  Dissolve  the  residue 
in  water  and  carry  out  the  double  dyeing  method,  as  described 
on  page  221. 

To  test  for  turmeric  add  to  a  portion  of  the  sample  three 
drops  of  saturated  boric  acid  solution,  one  small  drop  of  dilute 
(i  :io)  hydrochloric  acid,  and  a  piece  of  filter-paper  so  arranged 
that  it  is  only  half  immersed  in  the  liquid.  Evaporate  to 
dryness  on  the  water-bath.  In  the  presence  of  turmeric  the 
paper  will  be  colored  pink  and  the  test  may  be  confirmed  as 
described  on  page  188,  Excess  of  hydrochloric  acid  should  be 
avoided,  as  in  testing  for  boric  acid. 

Citral, — See  /.  Am.  Chem.  Soc,  1906,  1472. 


APPENDICES. 


APPENDIX  A. 

Table  I. 

TENSION    OF    AQUEOUS     VAPOR    IN    MILLIMETERS    OF    MERCURY    FROM 
0°    TO    30°. 9    C,    REDUCED    TO    0°    AND    SEA-LEVEL. 


o°.o. 

o».i. 

0».2. 

o°.3- 

o°.4. 

o°.5. 

o^.e. 

o».7. 

o°.8. 

o°.9. 

0° 

4-57 

4.60 

4.64 

4^67 

4.70 

4-74 

4.77 

4.80 

4.84 

4-87 

I 

4.91 

4.94 

4.98 

5.02 

5.05 

5.09 

5.12 

5.16 

5-20 

5.23 

2 

5.27 

5.31 

5.35 

5.39 

5.42 

5.46 

5.50 

5-54 

5-58 

5.62 

3 

5.66 

5 -70 

5.74 

5.78 

5.82 

5.86 

5.90 

5-94 

5-99 

6.03 

4 

6.07 

6. II 

6.15 

6.20 

6.24 

6.28 

6.33 

6.37 

6.42 

6.46 

5 

6.51 

6.55 

6.60 

6.64 

6.69 

6.74 

6.78 

6.83 

6.88 

6.92 

6 

6.97 

7.02 

7.07 

7.12 

7.17 

7.22 

7.26 

7.31 

7.36 

7.42 

7 

7.47 

7.52 

7-57 

7.62 

7.67 

7.72 

7.78 

7.83 

7.88 

7.94 

8 

7-99 

8.05 

8.10 

8.15 

8.21 

8.27 

8.32 

8.38 

8.43 

8.49 

9 

8.55 

8.61 

8.66 

8.72 

8.78 

8.84 

8.90 

8.96 

9.02 

9.08 

10 

9.14 

9.20 

9.26 

9-32 

9.39 

9-45 

9.51 

9.58 

9.64 

9.70 

II 

9-77 

9-83 

9.90 

9.96 

10.03 

10.09 

10.16 

10.23 

10.30 

10.36 

12 

10.43 

10.50 

10.57 

10.64 

10.71 

10.78 

10.85 

10.92 

10.99 

11.06 

13 

II  .14 

II. 21 

11.28 

11.36 

11-43 

11.50 

11.58 

11.66 

11-73 

II. 81 

14 

11.88 

11.96 

12.04 

12.12 

12. 19 

12.27 

12.35 

12.43 

12.51 

12.59 

15 

12.67 

12.76 

12.84 

12.92 

13.00 

13.09 

13.17 

13.25 

13-34 

13.42 

16 

13-51 

13.60 

13-68 

13.77 

13-86 

1395 

14.04 

14.12 

14.21 

14.30 

17 

14.40 

14.49 

14.58 

14.67 

14.76 

14.86 

14.95 

15.04 

15.14 

15-23 

18 

15.33 

15.43 

15-52 

15.62 

15.72 

15.82 

15.92 

16.02 

16.12 

16.22 

19 

16.32 

16.42 

16.52 

16.63 

16.73 

16.83 

16.94 

17.04 

17.15 

17.26 

20 

17.36 

17.47 

17.58 

17.69 

17.80 

17-91 

18. OS 

18.13 

18.24 

1S.35 

21 

18.47 

18.58 

18.69 

18.81 

18.92 

19.04 

19.16 

19.27 

19.39 

19.51 

22 

19.63 

19-75 

19.87 

19.99 

20.11 

20.24 

20.36 

20.48 

20.61 

20.73 

23 

20.86 

20.98 

21.  II 

21 .24 

21.37 

21.50 

21.63 

21.76 

21.89 

22.02 

24 

22.15 

22.29 

22.42 

22.55 

22.69 

22.83 

22.96 

23.10 

23-24 

23.38 

25 

23-52 

23.66 

23.80 

23 -94 

24.08 

24.23 

24.37 

24.52 

24.66 

24.81 

26 

24.96 

25.10 

25.25 

25.40 

25.55 

25.70 

25.86 

26.01 

26.16 

26.32 

27 

26.47 

26.63 

26.78 

26.94 

27. 10 

27.26 

27.42 

27.58 

27-74 

27.90 

28 

28.07 

28.23 

28.39 

28.56 

28.73 

28.89 

29.06 

29.23 

29.40 

2957 

29 

29.74 

29.92 

30.09 

30.26 

30.44 

30.62 

30.79 

30.97 

31.15 

31.33 

30 

31.51 

31.69 

31.87 

32.06 

32.24 

32.43 

32.61 

32.80 

32.99 

33-18 

236 


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240 


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APPENDIX    A. 


241 


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APPENDIX   A. 

Table  VII. 


TABLE     OF     HARDNESS,      SHOWING      THE      PARTS      OF     CALCIUM     CAR- 
BONATE   (CaCOj)    IN     1,000,000    FOR    EACH    TENTH    OF    A    CUBIC 
CENTIMETER    OF    SOAP    SOLUTION    USED. 


0.0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7    0.8 

0.9 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

cu.  cm. 

0.0 

0.0 

1.6 

3.2 

I.O 

4.8 

6.3 

7-9 

9-5 

II.  I 

12.7 

14-3 

15. 6|  16.9 

18.2 

2.0 

19.5 

20.8 

22.1 

23-4 

24.7 

26.0 

27 

3 

28.6!  29.9 

31-2 

3-0 

32.5 

33.8 

35-1 

36.4 

37.7 

39-0 

40 

3 

41.61  42.9 

44-3 

4.0 

45-7 

47.1 

48.6 

50.0 

51.4 

52-9 

54 

3 

55-7   57-1 

58.6 

5-0 

60.0 

61.4 

62.9 

64.3 

65-7 

67.1 

68 

6 

70.01  71.4 

72.9 

6.0 

74-3 

75-7 

77-1 

78.6 

80.0 

81.4 

82 

9 

84-3I  85-7 

87.1 

7.0 

88.6 

90.0 

91.4 

92.9 

94-3 

95-7 

97 

I 

98  6  100. 0 

101.5 

S.o 

IC3.0 

104.5 

106.0 

107.5 

109.0 

no. 5 

112 

0 

II3-5  1150 

116. 5 

9.0 

118. 0 

II9-5 

121. 1 

122.6 

124. 1 

125.6 

127 

I 

128.6  T30.1 

131-6 

10. 0 

133-1 

134.6 

136. 1 

137-6 

139- 1 

140.6 

142 

I 

143.7  T45-2 

146.8 

II  .0 

148. 4 

150  0 

151-6 

153-2 

154-8 

156.3 

157 

9 

159.5  161. 1 

162.7 

12.0 

164.3 

165.9 

167-5 

169.0 

170.6 

172.2 

173 

8 

175.4  !  177-0 

178.6 

I3-0 

180.2 

181. 7 

183-3 

184.9 

186.5 

188. 1 

189 

7 

191. 3  ^  192.9 

194.4 

14.0 

196.0 

197.6 

199.2 

200.8 

202.4 

204.0 

205 

6 

207.1  1  208.7 

210.3 

15-0 

211. 9 

213-5 

215. 1 

216.8 

218.5 

220.2 

221 

8 

223.5  225.2 

226.9 

Table  VIII. 

SHOWING    THE    NUMBER    OF     CUBIC     CENTIMETERS     OF    OXYGEN     DIS- 
SOLVED   IN     lOOC    CUBIC    CENTIMETERS    OF    W^ATER    WHEN 
SATURATED    AT    DIFFERENT    TEMPERATURES,    AS    CAL- 
CULATED   BY    WINKLER.* 


Deg.  Cent.' 

Cu.  Cm. 

Deg.  Cent. 

Cu.Cm. 

1 
Deg.  Cent. 

i 

Cu.  Cm. 

0 

10.187 

II 

7.692 

21 

6.233 

I 

9.910 

12 

7-518 

22 

6. 114 

2 

9-643 

1    '3 

7-352 

23 

5.999 

3 

9-387 

14 

7.192 

24 

5.886 

4 

9.142 

IS 

7-038 

25 

5  -  776 

5 

8.907 

16 

6.891 

26 

5-669 

6 

8. 682 

17 

6.750 

27 

5-564 

7 

8.467 

18 

6.614 

28 

5.460 

s 

8. 260 

19 

6.482 

29 

5-357 

9 

8.063 

!   20 

6.356 

30 

5.255 

10 

7-873 

Berichte,  22  i^i88g),  1 772. 


APPENDIX    A. 
Table  IX. 


243 


FOR    CORRECTING    THE     SPECIFIC    GRAVITY    OF    MILK    ACCORDING     TO 
TEMPERATURE.       ADAPTED    FROM    THE    TABLE    OF    VIETH. 

(Temperature  in  Degrees  Centigrade.) 


Specific 
Gravity. 

10° 

11° 

12° 

13° 

14° 

15° 

16°  ■ 

17 

18° 

19°    j    20° 

1.025 

24.1 

24-3 

24-5 

24.6 

24.7 

24.9 

25.1 

25 

3 

25.4 

25.6    25.9 

26 

251 

25.2 

25-4 

25.5 

25.7 

25.9 

26 

26 

3 

26.5 

26. 7[  27.0 

27 

26.1 

26.2 

26.4 

26.5 

26.7 

26.9 

27 

27 

4 

27-5 

27.71  28.0 

28 

27.0 

27.2 

27.4 

27.5 

27.7 

27.9 

28 

28 

4 

28.5 

28.71  29.0 

29 

2S.0 

28.2 

28.4 

28.5 

28.7 

28. 9 

29 

J 

29 

4 

29.5 

29. 8    30.1 

30 

29.0 

29.1 

29-3 

29-5 

29.7 

29.9 

30 

30 

4 

30.5 

30.8    31. 1 

31 

29.9 

30.1 

30.3 

30.4 

30.6 

30.9 

31 

2 

31 

4 

31-5 

3i-8|  32.2 

32 

30.9 

3I-I 

31.3 

31-4 

31.6 

31-9 

32 

2 

32 

4 

32.6 

32.9    33-2 

33 

31.8 

32.0 

32.3 

32.4 

32.6 

32-9 

33 

2 

33 

4 

33.6 

33-9    34-2 

34 

32-7 

33-0 

33-2 

33-4 

33.6 

33-9 

34 

2 

34 

4 

34-6 

34-9-  35-2 

35 

33.6 

33-9 

34.1 

34-4 

34.6 

34-9 

35.2 

35.4 

35.6 

35-9    362 

Directions. — Find  the  observed  gravity  in  the  left-hand  column.  Then 
in  the  same  line,  and  under  the  observed  temperature,  will  be  found  the 
corrected  reading. 


244 


APPENDIX    A. 

Table  X. 


PERCENTAGE     OF     ALCOHOL     FROM     THE     SPECIFIC     GRAVITY     AT 
I5°.5   C.       (HEHNER.) 


Percent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Sp.  Gr. 

Alcohol 

Alcohol 

Sp.  Gr. 

Alcohol 

Alcohol 

Sp.  Gr. 

Alcohol 

Alcohol 

15-5  C. 

by 

by 

i5°.5C. 

by 

by 

i5°.5C. 

by 

by 

1 

Weight. 

Volume. 

Weight. 

Volume. 

Weight. 

Volume. 

I.OOOO 

0.00 

0.00 

0-9999 

0.05 

0.07 

0.9959 

2-33 

2-93 

0.9919 

4-69 

5-86 

8 

O.II 

0-13 

8 

2-39 

3.00 

8 

4-75 

5-94 

7 

0.16 

0.20 

7 

2.44 

3-07 

7 

4-81 

6.02 

6 

0.21 

0.26 

6 

2.50 

3-14 

6 

4-87 

6.10 

5 

0.26 

0-33 

5 

2.56 

3.21 

5 

4-94 

6.17 

4 

0.32 

0.40 

4 

2.61 

3.28 

4 

5.00 

6.24 

3 

0-37 

0.46 

3 

2.67 

3-35 

3 

5-06 

6.32 

2 

0.42 

0-53 

2 

2.72 

3-42 

2 

5-12 

6.40 

I 

0-47 

0.60 

I 

2.78 

3-49 

I 

5-19 

6.48 

O 

0-53 

0.66 

0 

2.83 

3-55 

0 

5-25 

6-55 

0.9989 

0.58 

0.73 

0.9949 

2.89 

3-62 

0.9909 

5-31 

6.63 

8 

0.63 

0.79 

8 

2.94 

3-69 

8 

5-37 

6.71 

7 

0.68 

0.86 

7 

3.00 

3-76 

7 

5-44 

6.78 

6 

0.74 

0-93 

6 

3.06 

3-83 

6 

5-50 

6.86 

5 

0.79 

0.99 

5 

3.12 

3-90 

5 

5-56 

6.94 

4 

0.84 

1.06 

4 

3-18 

3-98 

4 

5.62 

7.01 

3 

0.89 

I-I3 

3 

3-24 

4-05 

3 

5.69 

7.09 

2 

0.95 

1. 19 

2 

3-29 

4.12 

2 

5-75 

7.17 

I 

1. 00 

1.26 

I 

3-35 

4.20 

I 

5.81 

7-25 

0 

1.06 

1-34 

0 

3-41 

4-27 

0 

5-87 

7-32 

0.9979 

I. 12 

1.42 

0.9939 

3-47 

4-34 

0.9899 

5-94 

7-40 

8 

1. 19 

1-49 

8 

3-53 

4-42 

8 

6.00 

7-48 

7 

1-25 

1-57 

7 

3-59 

4-49 

7 

6.07 

7-57 

6 

I-3I 

1-65 

6 

3-65 

4-56 

6 

6.14 

7.66 

5 

1-37 

1-73 

5 

3-71 

4-63 

5 

6.21 

7-74 

4 

1.44 

1. 81 

4 

3-76 

4.71 

4 

6.28 

7-83 

3 

1-50 

1.88 

3 

3.82 

4-78 

3 

6.36 

7.92 

2 

1-56 

1.96 

2 

3-88 

4-85 

2 

6.43 

8.01 

I 

1.62 

2.04 

I 

3-94 

4-93 

I 

6.50 

8.10 

0 

1.69 

2.12 

0 

4.00 

5.00 

0 

6.57 

8.18 

0.9969 

1.75 

2.20 

0.9929 

4.06 

5.08 

0-9889 

6.64 

8.27 

8 

1. 81 

2.27 

8 

4-12 

5.16 

8 

6.71 

8.36 

7 

1.87 

2.35 

7 

4.19 

5-24 

7 

6.78 

8.45 

6 

1.94 

2.43 

6 

4.25 

5-32 

6 

6.86 

8-54 

5 

2.00 

2.51 

5 

4.31 

5-39 

5 

6-93 

8.63 

4 

2.06 

2-58 

4 

4-37 

5-47 

4 

7-00 

8.72 

3 

2. II 

2.62 

3 

4-44 

5-55 

3 

7.07 

8.80 

2 

2.17 

2.72 

2 

4.50 

5-63 

2 

7-13 

8.88 

I 

2.22 

2.79 

I 

4-56 

5-71 

I 

7.20 

8.96 

0 

2.28 

2.86 

0 

4.62 

5-78 

0 

7-27 

9.04 

APPENDIX    A. 


245 


Table  X. — Continued. 

PERCENTAGE  OF  ALCOHOL. 


Sp.  Gr. 
iS°.5C. 


Per  cent 
Alcohol 

by 
Weight. 


0.9879 

8 

7 
6 

5 
4 

3 
2 

I 
o 

0.9869 

8 

7 
6 

5 
4 
3 
2 
I 
o 

0.9859 

8 

7 
6 

5 
4 
3 
2 

I 
o 

•0 .  9849 

8 

7 
6 

5 
4 
3 
2 
I 
o 

7 
6 

5 


Per  cent 
Alcohol 

by 
Volume. 


7-33 

7.40 
7-47 
7-53 
7.60 
7.67 

7-73 
7.80 

7-87 
7-93 

8.00 

8.07 
8.14 
8.21 
8.29 
8.36 

8.43 
8.50 

8.57 
8.64 

8.71 

8.79 
8.86 

8-93 
9.00 
9.07 
9.14 
9.  21 
9.29 
9-36 

9-43 

9-50 
9-57 
9.64 
9.71 

9-79 
9.86 

9-93 
10.00 
10.08 

10.15 

10.23 
10.31 
10-38 
10.46 


Sp.  Gr. 
i5°-5C. 


9.13 

9.  21 
9.29 

9-37 
9-45 
9-54 
9.62 

9.70 
9.78 
9.86 

9-95 

10.03 
10.12 
10.21 
10.30 
10.38 
10.47 
10.56 
10.65 
IO-73 

10.82 

10.91 
II  .00 
11.08 
II. 17 
II  .26 
11-35 
11.44 
11.52 
II  .61 

11.70 
11.79 
11.87 
11.96 
12.05 
12.13 
12.22 
12,31 
12.40 
12.49 

12.58 

12.68 
12.77 
12.87 
12.96 


Per  cent 
Alcohol 

by 
Weight. 


4 

3 
2 

I 
o 

0.9829 

8 

7 
6 

5 
4 

3 
2 

I 
o 

0.9819 

8 

7 
6 

5 
4 
3 
2 

I 
o 

0.9809 

8 

7 
6 

5 
4 
3 

2 

I 
o 

0.9799 

8 

7 
6 

5 
4 

3 

2 
I 


Per  cent 
Alcohol 

by 
Volume. 


10-54 
10.62 
10.69 
10.77 
10.85 

10.92 

11.00 
11.08 

II. 15 
11.23 
II. 31 
11.38 
11.46 
11-54 
II  .62 

11.69 

11.77 
11.85 
11.92 
12.00 
12.08 
12.15 
12.23 
12.31 
12.38 

12.46 

12.54 
12.62 
12.69 
12.77 
12.85 
12.92 
13.00 
13.08 
13-15 

13.23 

13-31 
13-38 
13-46 
13-54 
13.62 
13.69 
13-77 
13.85 
13.92 


Per  cent 
Alcohol 
i5°sC.  by 

Weight. 


13-05 
13-15 
13-24 
13-34 
13-43 

13-52 

13.62 
13.72 
13.81 
13.90 

13-99 
14.09 
14.18 
14-27 
14-37 

14.46 

14.56 
14.65 
14-74 
14-84 
14-93 
15-02 
15.12 
15.21 
15-30 

15-40 

15-49 
15-58 
15.68 

15-77 
15.86 

15-96 
16.05 
16.15 
16.24 

16.33 

16.43 
16.52 
16.61 
16.70 
16.80 
16.89 
16.98 
17.08 
17.17 


0.9789 

8 

7 
6 

5 
4 
3 
2 

1 
o 

0.9779 

8 

7 
6 

5 
4 
3 
2 
1 
o 

0.9769 

8 

7 
6 

5 
4 

3 

2 
I 
o 

0.9759 

8 

7 
6 

5 
4 
3 
2 

I 
o 


0.9749 

8 

7 
6 


Per  cent 
Alcohol 

by 
Volume. 


14.00 

14.09 
14.18 
14.27 
14.36 
14-45 
14.55 
14.64 

14-73 
14-82 

14.90 

15.00 
15-08 
15-17 
15-25 
15-33 
15-42 
15-50 
15-58 
15-67 

15-75 

15-83 
15-92 
16.00 
16.08 
16.15 
16.23 

16.31 
16.38 
16.46 

16.54 

16.62 
16.69 
16.77 
16.85 
16.92 
17.00 
17.08 
17-17 
17-25 

17-33 

17-42 
17-50 
17.58 
17.67 


17.26 

17-37 
17-48 
17-59 
17-70 
17.81 
17-92 
18.03 
18.14 
18.25 

18.36 

18.48 
18.58 
18.68 
18.78 
18.88 
18.98 
19.08 
19.18 
19.28 

19-39 

19-49 
19-59 
19.68 
19.78 
19.87 
19.96 
20.06 
20.15 
20.24 

20.33 

20.43 
20.52 
20.61 
20.71 
20.80 
20.89 
20.99 
21 .09 
21.19 

21.29 

20.39 
21.49 
21.59 
21.69 


246 


APPENDIX    A. 

Table  X. — Continued. 

PERCENTAGE  OF  ALCOHOL. 


Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Per  cent 

Sp   Gr. 

Alcohol 

Alcohol 

Sp.  Gr. 

Alcohol 

Alcohol 

Sp.  Gr. 

Alcohol 

Alcohol 

I5°.SC. 

by 

by 

i5°.5C. 

by 

by 

i5°.5C. 

by 

.r^y 

Weight. 

Volume. 

Weight. 

Volume. 

Weight. 

volume. 

4 

17-75 

21.79 

4 

20.17 

24.68 

4 

22.54 

27.49 

3 

17-83 

21.89 

3 

20.25 

24.78 

3 

22.62 

27.59 

2 

17.92 

2T.99 

2 

20.33 

24.88 

2 

22.69 

27.68 

I 

18.00 

2-.  09 

I 

20.42 

24.98 

I 

22.77 

27.77 

0 

18.08 

22.18 

0 

20.50 

25.07 

0 

22.85 

27.86 

0.9739 

18.15 

22.27 

0.9709 

20.58 

25.17 

0.9679 

22.92 

27-95 

8 

18.23 

22.36    j 

8 

20.67 

25.27 

8 

23.00 

28.04 

7 

18.31 

22.46 

7 

20.75 

25-37 

7 

23.08 

28.13 

6 

18.38 

22.55 

6 

20.83 

25-47 

6 

23-15 

28.22 

5 

18.46 

22.64 

5 

20  92 

25-57 

5 

23-23 

28.31 

4 

18.54 

22.73 

4 

21.00 

25-67 

4 

23.31 

28.41 

3 

18.62 

22.82 

3 

21 -08 

25   76 

3 

23-38 

28.50 

2 

18.69 

22.92 

2 

21-15 

25.86 

2 

23.46 

28.59 

I 

18.77 

23   01    j 

I 

21.23 

2595 

I 

23-54 

28.68 

0 

18.85 

23. 10   1 

° 

21,31 

26-04 

0 

23.62 

28.77 

0.9729 

18   92 

23.19 

0.9699 

21.38 

26.13 

0.9669 

23.69 

28.86 

8 

19  00 

23.28 

8 

21.46 

26   22 

8 

23-77 

28.95 

7 

19.08 

^?>-Z?> 

7 

21.54 

26.31 

7 

23-85 

29.04 

6 

19   17 

23.48 

6 

21.62 

26.40 

6 

23.92 

29.13 

5 

19-25 

23  58 

5 

21.69 

26.49 

5 

24,00 

29.22 

4 

19-33 

23,68 

4 

21.77 

26.58 

4 

24.08 

29.31 

3 

19.42 

23-78 

3 

21.85 

26.67 

3 

24-15 

29.40 

2 

19-50 

23.88 

2 

21.92 

26.77 

2 

24.23 

29.49 

I 

19.58 

23-98 

I 

22.00 

26.86 

I 

24.31 

29.58 

0 

19.67 

24.08 

0 

22.08 

26.95 

0 

24.38 

29.67 

0.9719 

19.75 

24.18 

0.9689 

22.15 

27.04 

0.9659 

24.46 

29.76 

8 

19.83 

24.28 

8 

22.23 

27-13 

8 

24.54 

29.86 

7 

19.92 

24-38 

7 

22.31 

27.22 

7 

24.62 

29.95 

6 

20.00 

24.48 

6 

22.38 

27-31 

6 

24.69 

30.04 

5 

20  08 

24.58 

5 

22.46 

27.40 

5 
4 
3 
2 

24-77 
24.85 
24.92 
25.00 

2,0. i2> 
30.22 

30.31 
30.40 

APPENDIX    A. 


247 


Table  XL 

EXTRACT  IN  WINE. 

Per  Cent  by  Weight. 
[According  to  Windisch.] 


Sp.  Gr 

Ex- 

Sp. Gr 

Ex- 

Sp. Gr 

Ex- 

1 

'Sp.  Gr 

Ex- 

Sp. Gr 

Ex- 

Sp. Gr 

Ex- 

tract. 

tract. 

tract. 

tract. 

tract 

tract. 

I  . 000c 

0.00 

I .020c 

S.17 

I .040c 

10. 35 

I .0600 

15.55 

I .080c 

20.78 

1 .  1000  26.04 

I  .0005 

0.13 

I .0205 

S.30 

I. 040s 

10.48 

I .0605 

15.68 

I .0805 

20.91 

I . loot 

26. 17 

I .OOIC 

0.26 

I .0210 

5.43 

r .0410 

10.61 

I .0610 

15.81 

I. 0810 

21 .04 

I . lOIC 

26.30 

1 .0015 

0.39 

1. 02 1 5 

5.56 

1.041S 

10.74 

I .0615 

15.94 

I .0815 

21 .  17 

I . 1015 

26.43 

I .0020 

0.52 

r .0220 

5.69 

I .0420 

10.87 

I .0620 

16.07 

I .0820 

21.31 

I . I02C 

26.56 

I .0025 

0.64 

I .0225 

5.82 

I .0425 

II  .00 

I .0625 

16.21 

I .0825 

21.44 

I . 1025 

26.70 

I .0030 

0.77 

I .0230 

5.94 

1.0430 

II. 13 

I .0630 

16.33 

I .0830 

21.57 

I . 1030 

26.83 

1.0035 

0.90 

10235 

6.07 

I  0435 

11.26 

1.063s 

16.47 

1.0835 

21  .  70 

I -1035 

26.96 

I .0040 

1.03 

I .0240 

6.20 

1.0440 

11.39 

1.0640 

16.60 

I .0840 

21  .83 

I . 1040 

27.09 

1.0045 

I. 16 

1.024s 

6.33 

1.0445 

H.52 

1.0645 

16.73 

1.0845 

21  .96 

1. 1045 

27.22 

I .0050 

1.29 

1.0250 

6.46 

1.0450 

II  .65 

1.0650 

16.86 

1.0850 

22  .09 

I . 1050 

27.35 

I -0055 

1.42 

I-025S 

6.59 

I .0455 

11.78 

I  0655 

16.99 

1-0855 

22  .22 

1. 1055 

27.49 

I .0060 

1.55 

I .0260 

6.72 

I .0460 

II. 91 

I .0660 

17.12 

1.0860 

22  .36 

I . 1060 

27.62 

1 .0065 

1.68 

I .0265 

6.8s 

1.046s 

12.04 

1.0665 

17.25 

1.0865 

22.49 

I . 1065 

27.7s 

1.0070 

i.8i 

I .0270 

6.98 

1.0470 

12.  17 

1.0670 

17.38 

I .0870 

22  .62 

I. 1070 

27.88 

1.0075 

1.94 

1.027s 

7. II 

1.0475 

12  .30 

1.067s 

17.51 

1.087s 

22.75 

I. 1075 

28.01 

1.0080 

2.07 

I .0280 

7.24 

I .0480 

12.43 

1.0680 

17.64 

1.0880 

22.88 

I. 1080 

28. IS 

1.0085 

2.19 

1.028s 

7.37 

1.0485 

12  .  56 

1.0685 

17.77 

1.0885 

23.01 

I. 1085 

28.28 

1 .0090 

2.32 

I .0290 

7.50 

1.0490 

12  .69 

I .0690 

17.90 

I .0890 

23.14 

I . 1090 

28.41 

1.009s 

2.45 

I. 0295 

7.63 

I .0495 

12.82 

1.0695 

18.03 

I .0895 

23.28 

I. 1095 

28.54 

I.OIOO 

2.58 

I .0300 

7.76 

I .0500 

12.95 

I .0700 

18. 16 

I . 0900 

23.41 

1 . 1 100 

26.67 

I. 0105 

2.71 

1.0305 

7.89 

1.0505 

13.08 

1.0705 

18.30 

I .0905 

23.54 

1.1105 

28.81 

I. Olio 

2.84 

I .0310 

8.02 

I .0510 

13.21 

I .0710 

18.43 

I .0910 

23.67 

I .  mo 

28.94 

1.0II5 

2.97 

1. 03 1 5 

8.14 

I .0515 

13.34 

I. 0715 

18.56 

1.0915 

23.80 

1.1115 

29.07 

I .0120 

3.10 

I .0320 

8.27 

I .0520 

13.47 

I .0720 

18.69 

I .0920 

23.93 

I . 1120 

29.20 

I. 0125 

3.23 

10325 

8.40 

1.052s 

13  .60 

1.0725 

18.82 

I .0925 

24.07 

I . 1125 

2933 

I. 0130 

3.36 

1.0330 

8.53 

1.0530 

13.73 

1.0730 

18.95 

1.0930 

24.20 

I . 1130 

29.47 

I.OI35 

3-49 

I  0335 

8.66 

1.0535 

13.86 

1.0735 

19.08 

I  0935 

24.33 

1.1135 

29.60 

1 .0140 

3.62 

1.0340 

8.79 

1.0540 

13.99 

1.0740 

19.21 

1.0940 

24.46 

I . 1140 

29.73 

1.0145 

3.7s 

I  0345 

8.92 

I .0545 

14. 12 

I.074S 

19.34 

1.0945 

24.59 

1.1145 

29.86 

I .0150 

3.87 

I. 0350 

905 

1.0550 

14.25 

1.0750 

19.47 

1 .0950 

24.72 

1 . 1150 

29.99 

1. 0155 

4.00 

I  0355 

9.18 

1.0555 

14.38 

I.07SS 

19.60 

1 .0955 

24.85 

I.I155 

30.13 

J  .0160 

4.13 

1.0360 

9.31 

I .0560 

14.51 

I .0760 

19.73 

I .0960 

24.99 

I .0165 

4.26 

1.036s 

9.44 

1.0565 

14.64 

I .0765 

19.86 

1.0965 

25.12 

1 .0170 

4.39 

1.0370 

9.57 

I .0570 

14.77 

I .0770 

20.00 

1.0970 

25.2s 

1.0175 

452 

10375 

9.70 

10575 

14.90 

I.0775 

20 .  12 

10975 

25.38 

I  .  0 1 80 

4.65 

I .0380 

9.83 

1.0580 

15  03 

I .0780 

20 .  26 

I .0980 

25.51 

I. 0185 

4.78 

1.0385 

9.96 

I  0585 

15.16 

1.0785 

20.39 

I .0985 

25.64 

I .0190 

4.91 

1.0390 

10.09 

I .0590 

15.29 

1.0790 

20.  52 

I .0990 

25.78 

I. 0195 

5  04 

I  0395 

10.  22 

I.0595 

15.42 

I .0795 

20.6s 

I  0995 

25.91 

248 


APPENDIX    A. 


Table  XII. 

TABLE      FOR      REDUCING      SUGAR      CONDENSED      FROM      THAT      OF 
MUNSON  AND  WALKER. 
(Expressed  in  milligrams.) 


d 

Q 

0 

X 

V 

3 

^ 

X 

p  3 
6 

, 

C/2 

+ 

A 

20 

, 

+ 

0 

Q 

> 

33 

0^ 

3^ 
0 

Q 

> 

2X 

10 

4.0 

4.5 

4.0 

5-9 

260 

117.6 

121. 4 

176.3 

203.9 

IS 

6.2 

6.7 

7.5 

9-9 

26s 

120  .0 

123-9 

179-7 

207.9 

20 

8.3 

8.9 

I0.9 

13.8 

270 

122.5 

126.4 

183.2 

211 .8 

25 

10.5 

II  .2 

14.4 

17.8 

275 

124-9 

128.9 

186.6 

215-8 

30 

12.6 

13-4 

17.8 

21.8 

280 

127-3 

131. 4 

190. 1 

219.7 

35 

14.8 

15.6 

21.3 

25-7 

285 

129.8 

133-9 

193-5 

223.7 

40 

16 . 9 

17.8 

24.7 

29.7 

290 

132.3 

136.4 

196.9 

227.6 

45 

19. 1 

20.  I 

28.2 

33-7 

295 

134.7 

138.9 

200. 4 

231 .6 

50 

21 .3 

22.3 

31.6 

37.6 

300 

137-2 

14I-5 

203.8 

235.5 

55 

23-5 

24.6 

35-0 

41-6 

30s 

139.7 

144.0 

207 .2 

239.5 

60 

25-6 

26.8 

38.4 

45-6 

310 

142.2 

146.6 

210.7 

243.  S 

65 

27.8 

29.1 

41  .9 

49-5 

315 

144.7 

149.  I 

214- 1 

247.4 

70 

30.0 

313 

45-4 

53-5 

320 

147-2 

151-7 

217.6 

251.3 

75 

32.2 

33-6 

48.8 

57.5 

32s 

149-7 

'54-^ 

221 .0 

255.3 

80 

34-4 

35-9 

52.3 

61.4 

330 

152.2 

156.8 

224.4 

259.3 

85 

36.7 

38.2 

55-7 

65.4 

335 

154.7 

159.4 

227.9 

263.2 

90 

38.9 

40.4 

59-2 

69 -3 

340 

157.3 

162  .0 

231.3 

267.1 

95 

41  .  I 

42.7 

62.6 

73-3 

345 

159.8 

164.6 

234.7 

271. 1 

100 

43-3 

450 

66.  I 

77-3 

350 

162  .4 

167.  2 

238.2 

275.0 

105 

45-5 

47-3 

69.5 

81.2 

355 

164.9 

169.8 

241 .6 

279.0 

no 

47-8 

49-6 

73-0 

85.2 

360 

167-S 

172.5 

245.1 

282  .9 

IIS 

50.0 

51-9 

76.4 

89.2 

365 

170.  I 

175-1 

248.5 

286.9 

I30 

52.3 

54-3 

79.8 

93-1 

370 

172.7 

177.7 

252.0 

290.8 

135 

54-5 

56.6 

83.3 

97.1 

375 

175-3 

180.4 

^55-4 

294.8 

130 

56.8 

58.9 

86.7 

loi  .0 

380 

177-9 

183.0 

258.8 

298.7 

13s 

590 

61.2 

90.2 

105.0 

385 

180.  s 

185.7 

262.3 

302.7 

140 

61.3 

63.6 

93-6 

109.0 

390 

183. I 

188.4 

265.7 

306.6 

145 

63.6 

659 

97-1 

1X2. 9 

395 

185.7 

191  .0 

269.  I 

310.6 

ISO 

65-9 

68.3 

100.5 

116. 9 

400 

188.4 

193.7 

272.6 

314. 5 

15s 

68.2 

70.6 

1040 

120.8 

405 

191  .0 

196.4 

376.0 

318.5 

160 

70.4 

730 

107.4 

124. S 

410 

193.7 

199.1 

279.5 

322.4 

165 

72.8 

75-3 

no. 9 

128.8 

415 

196.3 

201.8 

282.9 

326.3 

170 

75-1 

77-7 

II4-3 

132.7 

420 

199.0 

204.6 

286.3 

330.3 

175 

77-4 

80.1 

117.7 

136.7 

425 

201  .  7 

207.3 

289.8 

334.3 

180 

79-7 

82.5 

121 .2 

140.6 

430 

204.4 

210.0 

293.2 

338.3 

185 

82  .0 

84.9 

124.6 

144-6 

435 

207.  I 

212  .8 

296.6 

342.1 

190 

84.3 

87.2 

128.  1 

148.6 

440 

209.8 

215. 5 

300  .  I 

346.1 

195 

86.7 

89.6 

131.5 

152.5 

445 

212.5 

218.3 

303.5 

3SO.O 

200 

89.0 

92  .0 

I35-0 

156.5 

450 

21S-2 

221.1 

306.9 

353.9 

205 

91.4 

94-5 

138.4 

160.4 

455 

218.0 

223.9 

310.4 

357.9 

210 

93-7 

96.9 

141 .9 

164-4 

460 

220.  7 

226.7 

313.8 

361.8 

215 

96.1 

99-3 

145-3 

168.3 

465 

223.5 

229.5 

317-3 

365.8 

220 

98.4 

101  .  7 

148.7 

172.3 

470 

226.  2 

232.3 

320.7 

369.7 

225 

100.8 

I04-2 

152.2 

176.2 

475 

229.0 

235.1 

324.1 

373.7 

230 

103.2 

106.6 

155.6 

180.2 

480 

231.8 

237.9 

327.6 

377.6 

235 

105.6 

109.  I 

159-1 

184.2 

485 

234-6 

240.8 

331.0 

381. 5 

240 

108.0 

III. 5 

162  .  5 

188.1 

490 

237.4 

243-6 

334.4 

385.  S 

245 

no. 4 

114.0 

166.0 

192  .  I 

250 

112  .8 

116. 4 

169.4 

196.0 

255 

II5-2 

118. 9 

172  .8 

200.0 

APPENDIX    A. 

Table  XIIL 

EXTRACT    IN    P,EER-W(^RT. 

(According  to  Schultz  and  Ostermann.) 


249 


Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

Gravity  at 

I'er  cent 

Gravity  at 

Per  cent. 

Gravity  at 

Per  cent. 

Gravity  at 

I'er  ceni. 

15°  C. 

by  Weight. 

.5°C. 

by  Weight. 

15°  c. 

by  Weight. 

.5°C. 

by  Weight, 

I .0000 

0.00 

I    0235 

6.07 

1.0470 

11.89 

1.0705 

17.59 

1 .0005 

0.13 

1.0240 

6.19 

I    0475 

12. 

01 

I .0710 

17.70 

I .0010 

0.  26 

1.0245 

6.31 

I . 0480 

12. 

14 

I. 0715 

17.81 

I .0015 

0-39 

1.0250 

6.44 

1.0485 

12  . 

26 

I .0720 

17-93 

I .0020 

0.52 

I    0255 

6.58 

I . 0490 

12. 

38 

1.0725 

18.04 

I .0025 

0.66 

1.6260 

6.71 

1-0495 

12. 

50   1 

1.0730 

18.  15 

I . 0030 

0.79 

1.0265 

6.85 

1.0500 

12 

63 

I    0735 

18.26 

I    0035 

0.92 

I .0270 

6.99 

1-0505 

12 

75   1 

1.0740 

18.38 

I . 0040 

1.05 

1.0275 

7.12 

I. 0510 

12 

87    i 

I    0745 

18.49 

1.0045 

I. 18 

I .0280 

7.26 

I -05 1 5 

12 

99   1 

1.0750 

18.59 

1.0050 

I -31 

1.0285 

7  •  37 

1.0520 

13 

12 

I    0755 

1S.70 

I    0055 

1.44 

I .0290 

7.48 

1-0525 

13 

24 

I .0760 

18.81 

I .0060 

1.56 

I    0395 

7.60 

I  0530 

13 

36 

1.0765 

18.91 

I . 0065 

1.69 

I . 0300 

771 

I  0535 

13 

48 

1.0770 

19.02 

1.0070 

1.82 

I    0305 

7-82 

1.0540 

13 

61 

I    0775 

19.  12 

1.0075 

1-95 

I. 0310 

7-93 

I  0545 

13 

73 

T .0780 

19-23 

I .0080 

2.07 

IO315 

8.04 

I  0550 

i3 

86 

T.O785 

19-33 

I .0085 

2.20 

1.0320 

8.16 

i0555 

13 

98 

1.0790 

19-44 

I .0090 

2.33 

1-0325 

8.27 

1.0560 

14 

II 

1-0795 

19-56 

1.0095 

2.46 

1.0330 

8.40 

1-0565 

14 

23 

I      0800 

19.67 

I  .0100 

2.58 

1-0335 

8.53 

1.0570 

14 

36 

i . 0805 

19.79 

I  .0105 

2.71 

I . 0340 

8.67 

I  0575 

?4 

49 

I .0810 

19.91 

I  .01  10 

2.84 

I    0345 

8.80 

1.0580 

u 

62 

1.0815 

20.03 

I.0115 

2.97 

I    0350 

8.94 

1.0585 

14 

75 

I .0820 

20.  14 

I  .0120 

3.10 

I    0355 

9.07 

I . 0590 

U 

89 

1.0825 

20.  26 

I .0125 

3-23 

I . 0360 

9.21 

1-0595 

15 

02 

I .0830 

20.37 

I. 0130 

3-35 

I    0365 

9.34 

I . 0600 

15 

14 

I      0835 

20.48 

JO135 

3-48 

1.0370 

9-45 

I . 0605 

15 

25 

I . 0840 

20.59 

I  .0140 

3.61 

I    0375 

9-57 

I .0610 

15 

36 

1.0845 

20.  70 

I. 0145 

3-74 

1.0380 

9.69 

1 . 06 1 5 

15 

47 

I , 0850 

20.81 

I  .0150 

3.87 

1-0385 

9.81 

I .0620 

15 

58 

1.0855 

20.93 

IO155 

4.00 

1.0390 

9-92 

I .0625 

15 

69 

1 . 0860 

21.06 

I  .0160 

4-13 

1-0395 

10.04 

I . 0630 

15 

80 

1.0865 

21.19 

I. 0165 

4.26 

I .0400 

10. 16 

I  0635 

15 

92 

I .0870 

21.33 

I  .0170 

4-39 

1.0405 

10.27 

I . 0640 

16 

03 

1.0875 

21.43 

I. 0175 

4-53 

I .0410 

10.40 

1.0645 

16 

-14 

1.0880 

21.54 

1. 0180 

4.66 

I. 0415 

10.52 

I . 0650 

16 

•25 

1.0885 

21  .64 

1. 0185 

4-79 

I .0420 

10.65 

1-0655 

16 

-37 

I . 0890 

21.75 

I .0190 

4-93 

1.0425 

10.77 

I . 0660 

16 

-50 

1.0895 

21.86 

-   1. 0195 

5.06 

1.0430 

10.90 

I . 0665 

16 

.62 

I . 0900 

21.98 

1.0200 

5.20 

I    0435 

11.03 

1.0670 

16 

-74 

1.0905 

22.08 

1.0205 

5.33 

I . 0440 

II. 15 

1.0675 

16 

.86 

I. 0910 

22.  19 

I. 0210 

5-45 

1.0445 

11.28 

I . 0680 

16 

-99 

I. 0915 

22.30 

I. 0215 

5-57 

I    0450 

1 1 .40 

1.0685 

17 

.  II 

I .0920 

22.41 

1 .0220 

5  70 

I    0455 

1 1    53 

I . 0690 

17 

23 

I      0925 

22,52 

I .0225 

5.82 

I . 0460 

11.65 

I . 0695 

17 

•35 

I      0930 

22.63 

1.0230 

5-94 

1.0465 

11.77 

I .0700 

17 

-48 

I      0935 

22.73 

'SO 


APPENDIX    A. 


Table  XIII. — Continued. 


EXTRACT    IN    BEER-WORT. 
(According  to  Schultz  and  Ostermann.) 


Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

Specific 

Extract. 

Gravity  at 

Per  cent. 

Gravity  at 

Per  cent 

Gravity  at 

Per  cent. 

Gravity  at 

Per  cent. 

.5°C. 

by  Weight. 

15°  C. 

by  Weight. 

15°^- 

by  Weight 

.s°c. 

by  Weight. 

I . 0940 

22.84 

I . 1020 

24-53 

I . 1 100 

26.  27 

I. 1 180 

27.88 

0945 

22.94 

I. 1025 

24 

64 

I. 1 105 

26.37 

I. 1185 

27.98 

0950 

23-05 

I . 1030 

24 

74 

I  .  IIIO 

26.48 

I  . 1 1 90 

28.09 

0955 

23.16 

I -1035 

24 

85 

I  .  III5 

26.58 

I -"95 

28.  19 

0960 

23.27 

I . 1040 

24 

96 

I . 1 1  20 

26.68 

1 . 1 200 

28.28 

0965 

23-37 

I . 1045 

25 

07 

I  .  1125 

26.79 

I . 1205 

28.38 

0970 

23-48 

I . 1050 

25 

18 

I .  1 1  30 

26.89 

1 . 1210 

28.48 

0975 

23-59 

I -1055 

25 

29 

I-II35 

26.99 

1.1215 

28.58 

0980 

23.69 

I . 1060 

25 

40 

I . 1 1 40 

27.09 

I. 1220 

28.68 

0985 

23.80 

I . 1065 

25 

50 

I. 1 145 

27.19 

I. 1225 

28.78 

0990 

23.90 

I . 1070 

25 

61 

I . 1 1 50 

27.29 

I. 1230 

28.88 

0995 

24.01 

I. 1075 

25 

71 

I-II55 

27.38 

I .1235 

28.98 

1000 

24.11 

I . 1080 

25 

82 

I.  1 160 

27-48 

1 . 1 240 

29.08 

1005 

24.21 

I. 1085 

25 

93 

I.I165 

27-58 

I. 1245 

29.  18 

.  lOIO 

24.32 

I . 1090 

26 

-05 

I . II70 

27.68 

I. 1250 

29.28 

.1015 

24.43 

I . 1095 

26 

.16 

I-II75 

27.78 

I .1255 

29.38 

APPENDIX    A. 
LOGARITHMS   OF   NUMBERS. 


251 


n^ 

Proportional  Parts. 

£j2 

2  c 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

- 

— 



—  ,- 

1    !    1 

— . 

re  3 
^2 

1 

2 

3 

4 

5 

6 

|7 

8 

9 

10 

0000 

0043 

0086 

0128 

0170 

0212102530294 

0334 

0374 

4 

8 

12 

17 

21 

j25'2g 

133 

37 

II 

04140453 

0492 

0531 

0569 

0607  0645  0682 

0719 

0755 

4 

8 

11 

15 

19 

23,26 

30 

34 

12 

079210828 

o864'o899 

0934 

0969  1004  1038 

1072 

1 106 

0 

7 

10 

14 

I 

h 

24 

28 

31 

13 

ii39iii73 

1 206;  1 239 

1271 

130311335  1367 

1399 

1430 

3 

6 

10 

13 

16 

^9 

23 

26 

29 

14 

1461 

1492 

1523 

1553 

1584 

1614  1644  1673 

1703 

1732 

3 

6 

9 

12 

15 

18 

21 

24 

27 

15 

1761 

1790 

1818 

1847 

1875 

i 
1903  1931  1959 

1987 

2014 

3 

6 

8 

II 

14 

117 

20 

22 

25 

16 

2041 

2068 

2095 

2122 

2148 

2175I2201  2227 

2253 

2279 

3 

5 

8 

II 

13 

1618 

21 

24 

17 

2304 

2330 

2355 

2380 

2405 

2430  2455  24S0 

2504 

2529 

2 

5 

7 

10 

12 

is' 

1^7 

20 

22 

18 

2553 

2577 

2601 

2625 

2648 

2672  2695  2718 

2742 

2765 

2 

5 

7 

9 

12 

14 

16 

19 

21 

19 

2788 

2810 

2833 

2856 

2878 

2900 

29232945 

2967 

2989 

2 

4 

7 

9 

II 

13 

16 

18 

20 

20 

3010 

3032 

3054 

3075 

3096 

311831393160 

3181 

3201 

2 

4 

6 

8 

I 

13 

15 

17 

19 

21 

3222 

3243 

3263 

3284 

3304 

3324:3345  3365 

3385 

3404 

2 

4 

6 

8 

10 

12 

14 

16 

18 

22 

3424 

3444 

3464I3483 

3502 

3522  3541  3560 

3579 

3598 

2 

4 

6 

8 

10 

12 

14 

15 

17 

23 

3617 

3636 

3655,3674 

3692 

3711  37293747 

3766 

3784 

4 

6 

7 

9 

II 

13 

IS 

17 

24 

3802 

3820 

3838 

3856 

3874 

3892  3909  3927 

3945 

3962 

4 

5 

7 

9 

II 

12 

14 

16 

25 

3979 

3997 

4014 

403 1 '4048 

4065  4082  4099 

4116 

4133 

3 

5 

7 

9 

10 

12 

14 

15 

26 

415014166 

418314200  4216 

4232 '4249  4265 

4281 

4298 

3 

5 

7 

8 

10 

II 

13 

15 

27 

43144330 

4346  4362  4378 

4393 

4409  4425 

4440 

4456 

3 

5 

6 

8 

9 

" 

13 

14 

28 

4472I4487 

4502 145 1 8  4533 

4548 

4564  4579 

4594 

4609 

3 

5 

6 

8 

9 

" 

12 

'14 

29 

4624 

4639 

4654  4669  4683 

4698 

47134728 

4742 

4757 

3 

4 

6 

7 

9 

10 

12 

13 

30 

4771 

4786 

480048144829 

4843 

4857:4871 

4886 

4900 

3 

4 

6 

7 

9 

10 

II 

13 

31 

+914 

4928  4942 14955  4969 

4983 

4997  501 1 

5024 

5038 

3 

4 

6 

7 

810 

II 

12 

32 

5051 

5065  507915092  5105 

5119 

5132  5145 

5159 

5172 

3 

4 

5 

7 

8 

9 

II 

12 

33 

5185I5198521I152245237 

5250 

52635276 

5289 

5302 

3 

4 

5 

6 

8 

9 

10 

12 

34 

531553285340 

5353  5366 

1 

5378 

5391  5403 

5416 

5428 

3 

4 

5 

6 

8 

^ 

10 

II 

35 

5441  5453  5465 

5478  5490 

5502 

55145527 

5539 

5551 

2 

4 

5 

6 

7 

9 

10 

II 

36 

556355755587 

5599  561 1 

5623 

5635 

5647 

5658 

5670 

2 

4 

5 

6 

7 

8 

10 

11 

37 

5682I56945705 

57175729 

5740 

5752 

5763 

5775 

5786 

2 

3 

5 

6 

7 

8 

9 

lO 

38 

5798158095821 

5832 

5843 

5855 

58665877 

5888 

5899 

2 

3 

5 

6 

7 

8 

9 

10 

39 

591 1  5922 

5933 

5944  5955 

5966 

5977  5988 

5999 

6010 

2 

3 

4 

5 

7 

8 

9 

10 

40 

6021  6031 

6042 

6053  6064 

6075 

60856096 

6107 

6117 

2 

3 

4 

5 

6 

8 

9 

lO- 

41 

61286138:6149 

6160  6170 

6180 

6191  6201 

6212 

6222 

2 

3 

4 

5 

6 

7 

8 

9 

42 

6232!6243!6253 

6263  6274 

62S4 

6294:6304 

6314 

6325 

I 

2 

3 

4 

5 

6 

7 

8 

9 

43 

63356345 

6355 

6365 

6375 

63S5 

6395  6405 

6415 

6425 

2 

3 

4 

5 

6  7l 

8 

,  9 

44 

6435 

6444 

6454 

6464 

6474 

6484 

64936503 

6513 

6522 

2 

3 

4 

5 

6 

7 

8 

9 

45 

6532 

6542 

6551 

6561 

6571 

6580 

1 
6590  6599 

6609 

6618 

2 

3 

4 

5 

6 

7 

8 

9 

46 

66286637 

6646 

6656 

6665 

6675 

66846693 

6702 

6712 

2 

3 

4 

5 

6 

7 

7 

8 

47 

6721  6730 

6739 

6749 

6758 

6767 

67766785 

6794 

6803 

2 

3 

4 

5 

5 

6 

8 

48 

6812 

6821 

6830 

6839 

6848 

6857 

68666875, 

6884 

6893 

2 

3 

4 

4 

5 

6 

7 

8 

49 

6902 

69 1 1 

6920 

6928 

6937 

6946 

6955  6964 

6972 

6981 

2 

3 

'-^ 

4 

5 

6 

7 

8 

50 

6990 

6998 

7007 

7016 

7024 

7033 

7042  7050 

7059 

7067 

2 

•  3 

3 

4- 

5 

6 

■  % 

8 

51 

7076I7084 

7093 

7101 

7110 

7118 

71267135 

7143 

7152 

.2 

3 

3 

4 

3 

.  6'  .7! 

8 

52 

71607168 

7177 

7185 

7193 

7202 

7210  7218 

7226 

7235 

2 

2 

3 

-  4 

5 

.6 

'% 

7 

53  ■ 

72437251 

7259 

7267 

7275 

7284 

7292 

7300 

7308 

7316 

2 

2, 

3 

4 

5, 

:^ 

.6 

7 

54 

7324  7332 

7340 

7348  7356I 

7364 

7372 

7380  7388I7396I 

r  2I 

2 

3 

4 

5^ 

6 

6 

7 

.252 


APPENDIX    A. 


LOGARITHMS   OF    NUMBERS. 


2^ 

2  £ 

55 
56 
57 
58 
59 

60 
61 
62 

63 
64 

65 
66 

67 
68 
69 

70 

71 

72 

73 
74 

75 
76 

77 
78 

79 

80 
8i 
82 

83 
84 

85 
86 

87 

88 

89 

90 

91 
92 

93 
94 


84518457846318470 
8513I8519  8525*8531 
857318579)85858591 
863386398645:8651 


7404 
7482 
7559 
7634 
7709 

7782 
7853 
7924 
993 
8062 

8129 

8195 
8261 

8325 


7412 


'419 


74901749: 


7566 
7642 
7716 


7574 
7649 

7723 


7427 
7505 
7582 
7657 
7731 


7789  7796,7803 
786o7868'7875 
793ii79387945 
Soooj  8007  8014 
806918075  8082 


8i36|8i42;8i49  8i56 
8202J8209J8215  8222 
8267i8274'828o8287 

833ii8338;8344!835i 
8395  8401,8407  8414 


7435 
7513 
7589 
7664 

7738 

7810 

7882 
7952 
8021 
8089 


8476 

8537 
8597 
S657 


869218698:8704  8710  8716 


8751875687628768 

88088814-88208825 
8865'887i  88768882 


8921J8927 
8976  8982 


8932  8938 
8987,8993 


9031  903690429047 
9085  9090  9096  9101 

91381914319149:9154 
919119196  9201  9206 
92431924892539258 

9294'9299  9304  9309 
93451935093559360 


9395:9400^9405 
9445  9450  9455 
9494  9499  9504 


9542 
9590 
9638 
9685 
9731 


95  97779782 

96  98239827 


9547 
9595 
9643 
9689 
9736 


97 
98 
99 


98689872 
9912J9917 
99569961 


[9552 
9600 

9647 
9694 
9741 

9786 

9832 

9877 
9921 

9965 


9410 
9460 
9509 

9557 
9605 
9652 
9699 
9745 

9791 
9836 
9881 
9926 
9969 


8774 
S831 
8887 

8943 
899S 

9053 
9106 

9159 
9212 
9263 

9315 
9365 
9415 
9465 
9513 

9562 
9609 
9657 
9703 
9750 

9795 
9841 
9886 
9930 


7443  7451 
75207528 
759717604 
7672  7679 

7745 

78187825 
7889  7896 
9597966 
802818035 
8096  8102 

8162  8169 

82288235 
8293I8299 
8357  8363 
8420  8426 


7459  7466  7474 
75367543  7551 
7612  7619I7627 

7686  7694J7701 
7760  7767  7774 


8482 

8543 
8603 
8663 

8722 

8779 
8837 
8893 
8949 
9004 


78327839 
79037910 
7973:7980 
8041:8048 
8i09'8ii6 


7846 
7917 

7987 
8055 
8122 

8189 


8241  8248,8254 
8306  8312  8319 


8370,8376 
84328439 


84S8  8494'850o 
8549'8555:856i 
8621 
8681 
8739 


8609 
8669 

8727 


8785 
8842 
8899 

8954 
9009 


9058I9063 
911219117 


9165 
9217 
9269 

9320 
9370 
9420 
9469 
9518 


9170 
9222 


S615 
8675 
8733 


8791 

8848 
8904 
8960 
9015 


I 

18797  8802 

88548859 

8910  8915 

18965:8971 

9020  9026 


8382 
8445 

8506 

8567 
8627 
8686 
8745 


9069  9074 
9122I9128 
9175I9180 
9227I9232 


92749279:9284 


9079 
9133 
9186 
9238 
9289 


93259330:93359340 
9375  9380  9385  9390 
9425  9430  9435  9440 
9474  9479  9484  9489 
9523952895339538 


95669571 
961419619 
9661  9666 
97089713 
9754  9759 


9800 

9845 
9890 

9934 
997419978 


9805 
9850 
9894 
9939 
998  ^ 


9576 
9624 
9671 
9717 
9763 

9809 
9854 
9899 
9943 
9987 


9581 
9628 

9675 
9722 
9768 


9586 

9633 
9680 

9727 
9773 


9814  981 
9859J9863 
9903 1 9908 
9948,9952 
9991I9996 


1     2 


1  report ional  Parts. 


4    5 


APPENDIX    A. 

253 

ANTILOGARITHMS. 

Proportional  i  aits_ 

P.^ 

0 

1 

i> 

8 

4 

5 

6 

m 
4 

8 

» 

1:23 

15     6    7     8    9 

.00 

1 00c 

1002 

IOO« 

1007 

1005 

1012 

1014 

[IO16 

IOI9  l02l|o     0     I 

I     I     I     2     2     2 

.01 

1023 

1026 

1028  103c 

103.^ 

103  = 

103^ 

104c 

104; 

1045    0     0     I 

I     I     I     2     2     2 

.02 

1047 

105c 

1052  1054 

1057 

1059 

1062 

1064 

1067 

1069    0     0     I 

[     I     I     2     2     2 

.03 

1072 

1074 

107611079 

1081 

1084 

1086 

io8g 

IO91 

1094   001. 

I     I     2     2     2 

.04 

1096 

1099 

1 102 

1104 

1107 

1 109 

1 1 12 

1114 

I  I  17 

I  I  19    0     I     I 

12222 

•05 

II22 

I1125 

1127 

1 1 30 

1132 

1135 

1 138 

1 1 40 

1143  I  146    0     I     I     1 

12222 

.06 

II48.II5I 

11153 

1 1 56 

1159 

1161 

1 1 64 

1167 

I  169  I172    0     I     I     I 

12222 

.07 

ii75'ii78|ii8o 

1183 

1 186 

1 189 

1191 

1 194 

Ii97'ii99  0    I    I    I 

12222 

.08 

1 202  j  1 205  1208 

1211 

1213 

1216 

1219 

1222 

1225 

1227     Dili 

12223 

.09 

12301233 

1 

I236II239 

1242 

1245 

1247 

1250 

1253 

1256     Dili 

12223 

.10 

1259 

1262 

1265  1268 

1271 

1274 

1276 

1279 

1282 

1285     Dili 

12223 

.11 

1288 

1291 

1294  1297 

1300 

1303 

1306 

1309 

1312 

I3I5     Dili 

22223 

.12 

1318 

1321 

1324 

1327 

1330 

1334 

io3/ 

1340 

1343 

1346     0       I       I       I 

22223 

.13 

1349 

1352 

1355 

1358 

1361 

1365 

1368 

1371 

1374 

1377     Dili 

22233 

.14 

1380 

1384 

1387 

1390 

1393 

1396 

1400 

1403 

1406 

1409     Dili 

22233 

.15 

1413 

1416 

I4I9 

1422 

1426 

1429 

1432 

1435 

1439 

1442     0       I       I       I 

22233 

.16 

1445 

1449 

1452 

1455 

1459 

1462 

1466 

1469 

1472 

1476     0       1       I       I 

22233 

.17 

1479 

1483 

i486 

1489 

1493 

1496 

1500 

1503 

1507 

I5IO     0       I       I       I 

22233 

.18 

1514 

1517 

I52I 

1524 

1528 

1531 

1535 

1538 

1542 

1545     Dili 

22233 

.19 

1549 

1552 

1556 

1560 

1563 

1567 

1570 

1574 

1578 

1581      0       I       I        I 

22333 

.20 

1585 

1589 

1592 

1596 

1600 

1603 

1607 

1611 

1614 

I618     0       I        I        I 

22333 

.21 

1622 

1626 

1629 

1633 

1637 

1641 

1644 

1648 

1652 

1656     0       I       I       2 

22333 

.22 

1660 

1663 

1667 

1671 

1675 

1679 

1683 

1687 

1690 

1694     0       I       I       2 

22333 

.23 

1698 

1702 

1706 

1710 

1714 

1718 

1722 

1726 

1730 

1734     0       I        I        2 

22334 

.24 

1738 

1742 

1746 

1750 

1754 

175S 

1762 

1766 

1770 

1774     0       I        I        2 

22334 

.25 

1778 

1782 

1786 

1791 

1795 

1799 

1803 

1807 

1811 

1816     0       I        I        2 

22334 

.26 

1820 

1824 

1828 

1832 

1837 

1841 

1845 

1849 

1854 

I85S     0       I        I        2 

23334 

.27 

1862 

1866 

I87I 

1875 

1879 

1884 

1888 

1892 

1897 

I  901    .0112 

23334 

.28 

1905 

1910 

I9I^ 

1919 

1923 

1928 

1932 

1936 

1 941 

1945      0       I        I        2 

23344 

.29 

1950 

1954 

1959 

1963 

1968 

1972 

1977 

1982 

1986 

1 99 1   0    I    I    2 

23344 

.30 

1995 

2000 

2004 

:oo9 

2014 

2018 

2023 

2028 

2032 

2037  0    I    I    2 

23344 

.31 

2042 

2046 

2051 

2056 

2061 

2065 

2070 

2075 

2080 

2084  0    I    I    2 

23344 

.32 

2089 

2094 

2099 

2104 

2109 

2113 

2118 

2123 

2128 

2133  0    I    I    2 

23344 

.33 

2138 

2143 

214^ 

2153 

2158 

2163 

2168 

2173 

2178 

2183  0    I    I    2 

23344 

.34 

2188 

2193 

219' 

2203 

220S 

2213 

2218 

22232228I 

2234  I    I    2    2 

3     3     4     4     5 

.35 

2239 

2244 

2249 

2254 

2259 

2265 

2270 

2275 

2280 

2286  I    I    2    2 

3     3     4     4     5 

.36 

2291 

2296 

2301 

2307 

2312 

2317 

2323 

2328 

2333 

2339  I    I    2    2 

3     3     4     4     5 

.37 

2344 

2350 

2355 

2360 

2366 

2371 

2377 

2382 

2388 

2393  I    I    2    2 

3     3     4     4     5 

.38 

2399 

2404 

24IC 

2415 

2421 

2427 

2432 

2438 

2443 

2449  1122 

3     3    4     4     5 

.39 

2455 

2460 

246C 

2472 

2477 

2483 

2489 

2495 

250c 

2506  112- 

3     3     4     5     5 

.40 

2512 

2518 

252: 

2529 

2535 

2541 

2547 

2553 

2559 

2564  I    I    2    2 

34455 

.41 

2570 

2576 

2582 

2588 

2594 

2600 

2606 

2612 

2618 

2624  I    I    2    2 

3     4     4     5     5 

.42 

2630 

2636 

2642 

2649 

2655 

2661 

2667 

2673 

2679 

2685  1122 

3     4     4     5'' 

.43 

2692 

2698 

2704 

2710 

2716 

2723 

2729 

2735 

2742 

2748      I        T       2       3 

3     4     4     5^' 

•  44 

2754 

2761 

2767 

2773 

2780 

2786 

2793 

2799 

2  80s 

2812     I       I       2      3 

3     4     4     5     (> 

.45 

2818 

2825 

2831 

2838 

2844 

2851 

2858 

2864 

2871 

2877      1123 

34556 

.46 

2884 

2891 

2897 

2904 

2911 

2917 

2924 

2931 

2938 

2944      I       I       23 

34556 

•47 

2951 

2958 

2965 

2972 

2979 

2985 

2992 

2999 

3006 

3013     I       I       2       3 

34556 

.48 

3020 

3027 

3034 

3041 

3048 

3055 

3062 

3069 

3076 

3083      1       T       2       3 

44566 
44566 

•49 

^090 

3097 

^lO'; 

^112 

71  19 

■^126 

3133 

3141 

3148    ^IS^I    T    1    T    !    2I    3 

254 


APPENDIX    A. 
ANTILOGARITHMS. 


50 
51 

52 
53 
.54 
.55 
.56 
.57 
.58 
.59 

.60 
.61 
.62 
.63 
.64 
.65 
.66 

.67 
.68 

.69 

70 

71 

72 

73 

'4 

.75 

76 

■  77 
.78 

.79 

.80 
I 

.82 
^83 
.84 
.85 
.86 
.87 


.90 

.91 
.92 

.93 
.94 
95 
.96 
.97 
.98 
.99 


3162 

3236 
^?>  1 1 
3388 
3467 
3548 
3631 
3715 
3802^ 
3890] 


3170 

3243 
3319 
3396 
3475 
3556 
3639 
3724 
3811 
3899 


3981 1 3990 
4074  4083 
41694178 
4266  4276 
43654375 
4467  4477 


4571 
4677 
4786 
4898 

5012 
5129 
5248 
5370 
5495 
5623 
5754 


6026 
6166 

6310 

6457 
6607 
6761 
6918 
7079 
7244 
7413 
7586 
7762 

7943 
8128 
8318 
85 1 1 
8710 

8913 
9120 

9333 
9550 
9772 


4581 
4688 

4797 
4909 

5023 
5140 
5260 

5383 
5508 
5636 
5768 
5902 

6039 
6180 

6324 
6471 
6622 
6776 
6934 
7096 
7261 
7430 
7603 
7780 

7962 

8147 
8337 
8531 
8730 
8933 
9141 

9354 
9572 
9795 


3177 
3251 
3327 
3404 
3483 
3565 
3648 
3733 
3819 
3908 

3999 
4093 

4188 

4285 
4385 
4487 
4592 
4699 
4808 
4920 

5035 
5152 
5272 
5395 
5521 
5649 
5781 
5916 
6053 
6194 

6339 
6486 

6637 
6792 
6950 
7112 

7278 
7447 
7621 
7798 

7980 
8166 
8356 
8551 
8750 
8954 
9162 
9376 
9594 
9817 


3184 

3258 
3334 
3412 
3491 
3573 
3656 
3741 
3828 

391 

4009 
4102 
4198 
4295 
4395 
4498 
4603 
4710 
4819 
4932 

5047 
5164 
5284 
5408 
5534 
5662 

5794 
5929 
6067 
6209 

6353 
6501 
6653 
6808 
6966 
7129 
7295 
7464 
7638 
7816 

7998 

8185 

8375 

8570 

8770 

8974 

9183 

9397j94i9 

9616  96^8 

9840'9^3 


3192 
3266 

3342 

3420 

3499 

3581 

3664 

S750 

383 

3926 

4018 
4111 
4207 

4305 
4406 
4508 

4613 
4721 

4831 
4943 

5058 
5176 
5297 
5420 
5546 
5675 
5S08 

5943 
6081 
6223 

6368 
6516 
6668 
6823 
6982 
7145 
73" 
7482 

7656 
7834 

8017 
8204 
8395 
8590 
8790 
8995 
9204 


3199 

3273 
3350 


3206 

3281 
3357 


3428J3436 
3508' 35 16 
^589  359 


3673 
3758 
3846 
3936 


3681 
3767 
3855 
3945 


4027  4036 
4121  4130 

4217,4227 
43i5;4325 
44164426 
45194529 
46244634 
4732]4742 
4842:4853 
49554966 

5070  5082 
5188J5200 
53095321 
5433  5445 


5559 
5689 


5572 
5702 


5821  5834 
5957,5970 
609516109 
6237|6252 

638316397 
6531:6546 


6683 
6839 
6998 
7161 
7328 
7499 


6699 

6855 
7015 
7178 
7345 
7516 


76747691 

7852  7870 

5o35|8o54 
H222J8241 
8414^8433 
86 10  8630 
88io'883i 
9016  9036 
92269247 
9441,9462 
9661  9683 
9886  9908 


32 

3289 

3365 

3443 

3524 

3606 

3690 

3776 

3864 

3954 


8 


4  322IJ3228 
^296,3304 
33733381 


H5I 
3532 
3614 
3698 
3784 
3873 
3963 


4046 '4055 


4140 
4236 
4335 
4436 
4539 
4645 
4753 
4864 


4150 
4246 
4345 
4446 
4550 
4656 
4764 
4875 


4977  4989 


5093 

5212 

5333 
5458 
5585 
5715 
5848 
5984 
6124 
6266 


6412 
6561 
6714 
6871 
7031 
7194 
7362 
7534 
7709 
7889 

8072 
8260 

8453 
8650 
8851 

9057 
9268 

9484 
9705 
9931 


5105 
5224 
5346 
5470 
5598 
5728 
5861 
5998 
6138 
6281 

6427 
6577 
6730 
6887 
7047 
7211 
7379 
7551 
7727 
7907 

8091 
8279 
8472 
8670 
8872 
9078 
9290 
9506 
9727 
9954 


3459 

3540 

3622 

370 

3793 

3882 

39 

4064 
4159 

4256 
4355 
445 
4560 
4667 
4775 
887 

dOOO 

511 

5236 

5358 

5483 

5610 

5741 

5875 

6012 
6152 
6295 

6442 
6592 
6745 
6902 

7063 

7228 
7396 

7568 

745 
7925 

8110 
299 
8492 
8690 
8892 
9099 
9311 
9528 
9750 
9977 


Proportional  Parts. 


1 

2 

3 

4 

5 

6 

7 

8 

9 

I 

2 

3 

4 

5 

6 

2 

2 

3 

4 

5 

6 

2 

2 

3 

4 

5 

6 

2 

2 

3 

4 

6 

6 

2 

2 

3 

4 

6 

6 

2 

2 

3 

4 

6 

7 

2 

3 

3 

4 

6 

7 

8 

2 

3 

3 

4 

6 

7 

8 

2 

3 

4 

4 

6 

7 

8 

2 

2 

4 

5 

6 

7 

8 

2 

3 

4 

5 

6 

6 

7 

8 

2 

3 

4 

5 

6 

8 

9 

2 

3 

4 

5 

6 

8 

9 

2 

3 

4 

5 

6 

8 

9 

2 

3 

4 

5 

6 

8 

9 

2 

3 

4 

5 

6 

8 

9 

2 

3 

4 

5 

6 

9 

10 

2 

3 

4 

5 

7 

8 

9 

10 

2 

3 

4 

6 

7 

8 

9 

10 

2 

3 

5 

6 

7 

8 

9 

10 

2 

4 

5 

6 

7 

8 

9 

II 

2 

4 

5 

6 

7 

8 

10 

11 

2 

4 

5 

6 

7 

9 

10 

II 

3 

4 

5 

6 

8 

9 

10 

II 

.3 

4 

5 

6 

8 

9 

lO 

12 

3 

4 

5 

7 

8 

9 

10 

12 

3 

4 

5 

7 

8 

9 

II 

12 

3 

4 

5 

7 

8 

10 

II 

12 

3 

4 

6 

7 

8 

10 

II 

13 

3 

4 

6 

7 

9 

10 

II 

13 

3 

4 

6 

7 

9 

10 

12 

13 

3 

5 

6 

8 

9 

II 

12 

14 

3 

5 

6 

8 

9 

II 

12 

14 

3 

5 

6 

8 

9 

II 

13 

14 

3 

5 

6 

8 

10 

II 

13 

IS 

3 

5 

7 

8 

10 

12 

13 

IS 

3 

5 

7 

8 

10 

I  2 

13 

IS 

3 

5 

7 

9 

10 

12 

14 

16 

4 

5 

7 

9 

II 

12 

14 

16 

4 

5 

7 

9 

" 

13 

14 

16 

4 

6 

7 

9 

11 

13 

15 

17 

4 

6 

8 

9 

II 

13 

15, 

17 

4 

6 

8 

10 

12 

14 

15 

17 

4 

6 

8 

iO 

12 

14 

16 

18 

4 

6 

8 

10 

I  2 

14 

16 

18 

4 

6 

8 

10 

12 

IS 

17 

19 

4 

6 

8 

11 

13 

15 

17 

19 

4 

7 

9 

II 

13 

IS 

17 

20 

4 

7 

9 

1 1 

13 

i6 

18 

20 

5 

7 

0 

II 

M' 

16 

18 

20 

APPENDIX   B. 

REAGENTS. 
AIR    ANALYSIS. 

Barium  Hydroxide. — A  solution  containing  about  4  grams 
of  BaO  and  0.2  gram  of  BaCU  to  the  liter,  (i  c.c.  =  1  mg. 
CO2,  approximately.) 

Sulphuric  Acid. — Dilute  45.45  c.c.  of  normal  sulphuric 
acid  to  one  liter,  (i  c.c.  =  1  mg.  COj.)  To  standardize  the 
solution  measure  25  c.c.  into  a  weighed  platinum  dish,  add 
dilute  ammonia-water  in  slight  excess,  evaporate  to  dryness 
on  the  water-bath,  and  dry  at  120°  C.  to  constant  weight. 

Standard  Lime-water. — (For  Popular  Tests.) — Shake  one 
part  of  freshly  slaked  lime  with  20  parts  of  distilled  water  for 
twenty  minutes  and  let  the  solution  stand  overnight  or  until 
perfectly  clear.  This  solution  should  be  very  nearly  equiva- 
lent to  the  above  standard  sulphuric  acid.  To  a  liter  of  dis- 
tilled water  add  5  c.c.  of  a  solution  of  0.7  gram  of  phenol- 
phthalein  in  100  c.c.  of  50  per  cent,  alcohol  and  add  lime- 
water  drop  by  drop  until  a  slight  permanent  pink  color  is 
produced.  Add  12.6  c.c.  of  the  above  calcium  hydroxide 
solution.  The  resulting  solution  is  the  standard  lime-water 
used  for  the  tests. 

WATER    ANALYSIS. 

For  Ammonia. — Water  Free  from  Ammonia. — The  am- 
monia-free water  used  in  this  laboratory  is  made  by  redis- 
tilling distilled  water  from  a  solution  of  alkaline  permangan- 

255 


2s6 


APPENDIX    B. 


ate  in  a  steam-heated  copper  still.  The  apparatus  used  is 
shown  in  Fig.  15.  Only  the  middle  portion  of  the  distillate 
is  collected.  Oftentimes  the  distillate  from  a  good  spring- 
water  may  be  used. 

A^esslers  Reagent. — Dissolve  61,750  grams  KI  in  250  c.c. 
distilled  water  and  add  a  cold  solution  of  HgCU  which  has 
been  saturated  by  boiling  an  excess  of  the  salt  and  allowing 
it  to  crystallize  out.  Add  the  HgCL  cautiously  until  a  sl'ght 
permanent   red   precipitate   (Hgig)    appears.      Dissolve   this 


Fig.    15. — Still  for  Ammonia-free  Water. 


slight  precipitate  by  adding  0.750  gram  powdered  KI.  Then 
add  150  grams  of  KOH  dissolved  in  250  c.c.  of  water.  Make 
up  to  the  liter  and  allow  it  to  stand  overnight  to  settle.  This 
solution  should  give  the  required  color  with  ammonia  within 
five  minutes,  and  should  not  precipitate  within  two  hours. 

Alkaline  Permanganate. — Dissolve  233  grams  of  the  best 
stick  potash  in  350  c.c.  of  distilled  water.     Filter  this  strong 


APPENDIX    13.  257 

solution,  if  necessary,  through  a  layer  of  glass  wool  on  a  por- 
celain filter-plate.  Dilute  with  700  to  750  c.c.  of  distilled 
water  to  a  sp.  gr.  of  1.125,  add  8  grams  of  potassium  per- 
manganate crystals,  and  boil  down  to  one  liter  to  free  the 
solution  from  nitrogen.  Each  new  lot  of  reagent  must  oe 
tested  before  being  used,  but  when  the  chemicals  used  are  all 
good  there  should  be  no  correction  needed  for  ammonia  in 
the  solution. 

Standard  Ammonia  Solution. — Dissolve  3.8215  grams 
chemically  pure  NH4CI  in  a  liter  of  water  free  from  ammo- 
nia. This  is  the  strong  solution  from  which  the  s  andard 
solution  is  made  by  diluting  10  c.c.  to  a  liter  wi.h  w^a.e:  free 
from  ammonia.  One  c.c.  of  the  standard  solution  =  o.o:coi 
gram  nitrogen.  This  solution,  like  the  nitrite  standard  and 
other  dilute  solutions,  must  be  preserved  in  sterijzcd  bott  es 
protected  from  dust  and  organic  matter. 

For  Nitrites. — Standard  Nitrite  Solution. — The  pure  sil- 
ver nitrite  used  in  making  this  solution  is  prepared  by  the 
double  decomposition  of  silver  nitrate  and  potassium  nitrite, 
and  repealed  crystallizations  from  water  of  the  rather  diffi- 
cultly soluble  silver  nitrite,  i.i  grams  of  this  silver  nitrite 
are  dissolved  in  nitrite-free  water,  the  silver  completely  pre- 
cipitated by  the  addition  of  the  standard  salt  solution  used  in 
the  determination  of  chlorine,  and  the  solution  made  up  tO' 
I  liter.  100  c.c.  of  this  strong  solution  are  diluted  to  i  liter,. 
and  10  c.c.  of  this  last  solution  again  diluted  to  i  liter.  The 
final  solution  is  the  one  used  in  preparing  standards,  i  c.c. 
=  0.0000001  gram  nitrogen. 

Sidpkanilic  Acid. — Dissolve  3.3  grams  sulphanilic  acid 
ii  750  c.c.  of  water  by  the  aid  of  heat,  and  add  250  c.c. 
glacial  acetic  acid. 

Naphtylamine  Acetate. — Boll  0.5  gram  of  ^-naphtylamine 
ill  100  c.c.  of  u  ater  in  a  small  Erlenmever  fiask  for  about  five 


258 


APrENDlX    B. 


minutes,  filter  through  a  plug  of  washed  absorbent  cotton, 
add  250  c.c.  glacial  acetic  acid,  and  dilute  to  a  liter. 

For  Nitrates. — Standard  Nitrate  Solution. — Dissolve 
0.720  gram  of  pure  recrystalHzed  KNO3  in  i  liter  of  water. 
Evaporate  10  c.c.  of  this  strong  solution  cautiously  on  the 
water-bath,  moisten  quickly  and  thoroughly  with  2  c.c.  of 
phenol-disulphonic  acid,  and  dilute  to  i  liter  for  the  stand- 
ard solution.      I  c.c.  =0.000001  gram  nitrogen. 

Phenol-disulphonic  Acid. — Heat  together  3  grams  syn- 
thetic phenol  with  37  grams  pure,  concentrated  H2S0^  in  a 
boiling-water  bath  for  six  hours. 

For  Kjeldahl  Process. — Sulphuric  Acid. — Sp.  gr.  1.84. 
This  should  be  free  from  nitrogen.  May  be  obtained  from 
Baker  and  Adamson,  Easton,  Pa. 

Potassium  Hydroxide. — Dissolve  350  grams  of  the  best 
stick  potash  in  ..25  liters  of  water  and  boil  down  to  some- 
thing less  thai  a  liter  with  3  grams  of  permanganate  crys- 
tals. When  cold,  dilute  to  a  liter  with  water  free  from  am- 
monia. 

For  Phosphates. — Ammonium  Molyhdate.—D\s>so\ve  50 
grams  of  the  pure  neutral  salt  in  a  liter  of  distilled  water. 

Nitric  Acid  (sp.  gr.  1.07). — One  part  of  acid  (sp.  gr.  1.42) 
to  five  parts  of  water. 

Standard  Phosphate  Solution. — Dissolve  o  5324  gram  of 
pure  crystallized  sodium  phosphate  (Na2HP04.i2H20)  in 
freshly  distilled  water,  add  100  c.c.  of  nitric  acid  (1.07),  and 
dilute  to  I  liter,  i  c.c.  =0.0001  gram  P2O5.  The  solution 
keeps  without  change  for  several  months  if  preserved  in 
well-stoppered  bottles  of  hard  glass ;  after  a  longer  time  it 
becomes  slightly  stronger,  owing  to  the  silica  dissolved  from 
the  glass. 

For  Chlorine. — Salt  Solution. — Dissolve  16.48  grams  of 
fused  NaCl  in  a  liter  of  distilled  water.     For  the  standard 


APPENDIX    R.  259 

S()lii:ion   dilute    100  c.c.  of  this  strong   solution   to    i    liter. 
I  c.c.  =0.001  i^ram  chlorine. 

Silver  Nitrate. — Dissolve  about  2.42  grams  of  AgNOg  (dry 
crystals)  in  i  liter  of  chlorine-free  water,  i  c.c.  =  .0005  ^ram 
CI,  approximately.     Standardize  against  the  NaCl  solution. 

Potassium  Chromate. — Dissolve  50  grams  neutral  K^CrO 
in  a  little  distilled  water.    Add  enough  AgNOg  to  produce  a 
slight  red  precipitate.     Filter  and  make  the  filtrate  up  to  a 
liter  with  water  free  from  chlorine. 

Milk  of  Alumina  for  Decolorization. — Dissolve  125  grams 
of  potash  or  ammonia  alum  in  a  liter  of  distilled  water.  Pre- 
cipitate the  Al(OH)3  by  the  cautious  addition  of  NH4OH. 
Wash  the  precipitate  in  a  large  jar  by  decantation  until  free 
from  chlorine,  nitrites,  and  ammofiia. 

For  Hardness. — Standard  Calcium  Chloride  Solution. — 
Dissolve  0.200  gram  of  pure  Iceland  spar  in  dilute  HCl,  tak- 
ing care  to  avoid  loss  by  spattering,  and  evaporate  to  dryness 
several  times,  to  remove  the  excess  of  acid.  Dissolve  the 
calcium  chloride  thus  formed  in  i  liter  of  water. 

Standard  Soap  Solution. — Dissolve  100  grams  of  the  best 
white,  dry  castile  soap  !n  a  liter  of  80  per  cent,  alcohol.  Of 
this  strong  solution  dissolve  75-100  c.c.  in  a  liter  of  70  per 
cent,  alcohol.  This  solution  must  have  70  per  cent,  alcohol 
added  to  it  until  14.25  c.c.  of  it  give  the  required  lather  with 
50  c.c.  of  the  above  CaCl2  solution. 

Erythrosinc  Indicator. — Dissolve  o.i  gram  of  erythrosine 
in  I  liter  of  water. 

For  Iron. — Standard  Iron  Solution. — Dissolve  0.86  gram 
of  ferric  ammonium  alum,  (NH^)2S04.Fe2(S04)3.24H20,  or 
a  corresponding  amount  of  the  potassium  salt  in  500  c.c.  of 
water,  add  5  c.c.  HNO3  (i-2o),  and  dilute  to  i  liter,  i  c.c.  = 
0.000  T  gram  Fe. 

Potassium  Sulphocyanide. — 5  grams  per  liter. 


26o  APPENDIX    B. 

Hydrochloric  Acid. — i  part  HCl  (sp.  gr.  1.20)  to  i  part  of 
water. 

Potassium  Permanganate. — 5  grams  KMn04  in  i  liter  of 
water. 

For  Dissolved  Oxygen. — (a)  48  grair.s  of  MnS04.4H20  in 
100  c.c.  of  water;  (b)  360  graTS  of  XaOH  and  100  grams  of 
KI  in  I  liter  of  water;   (c)  HCl,  sp.  gr.  1.20 

Sodium  Thios'ilphatc  Solution. — DissoU-e  25  grams  of  Dnre 
recrystallized  sodium  thiosulphate  in  i  liter  of  water.  Dilute 
200  c.c.  to  I  liter  and  standardize  against  a  known  KsCraOj 
solution. 

For  Lead. — Standard  Lead  Solution. — To  a  strong  solu- 
tion of  lead  acetate  add  a  slight  excess  of  H2SO4,  filter  off 
and  wash  the  precipitate.  >  Dissolve  it  in  ammonium  acetate 
solution,  made  by  neutralizing  glacial  acetic  acid  with  strong 
ammonia.  Make  up  to  a  known  volume  and  de::ermine  the  lead 
in  an  aliquot  part  by  precipitating  with  KoCrgO^  and  weigh- 
ing the  lead  chromate.  Dilute  an  aliquot  part  to  make  a  con- 
venient standard,  say  about  i  c.c.  =  o.ooi  gram  of  Pb. 

FOOD    ANALYSIS. 

Acid  Mercuric  Nitrate. — Dissolve  mercury  in  double  its 
weight  of  nitric  acid  (sp.  gr.  1.42)  and  dilute  the  solution 
with  five  times  its  volume  of  water. 

Pumice. — Bits  of  ignited  pumice,  about  the  size  of  a  pea, 
dropped  while  hot  into  water  and  bottled  for  use. 

Alcohol  (for  Reichert-Meissl  method). — 95  per  cent,  alcohol 
redistilled  from  potassium  hydroxide. 

Potassium  Hydroxide  (for  Reichert-Meissl  method). — One 
part  good  quality  caustic  potash  dissolved  in  one  part  of 
water. 

Iodine  Solution  (for  Hanus'  method). — This  is  conven- 
iently made  up  according  to  the   directions  of  Hunt.*     Dis- 

*  J .  Soc.  Cliem.  Ind.,  21  {igo2),  454. 


APPENDIX  B.  26  r 

solve  13.2  grams  iodine  in  i  liter  of  glacial  acetic  acid  (99  per 
cent.,  showing  no  reduction  with  bichromate  and  sulphuric 
acid).  This  will  best  be  done  by  adding  the  acetic  acid  in 
portions  and  heating  on  the  water-bath  with  frequent  shaking. 
To  the  cold  solution  add  enough  bromine  to  double  the  halogen 
content,  as  shown  by  titration.  Three  c.c.  of  bromine  is  suffi- 
cient.    A  slight  excess  of  iodine  is  not  detrimental. 

Potassium  Iodide. — Dissolve  200  grams  of  potassium  iodide 
in  I  liter  of  water. 

Anhydrous  Ether. — Wash  ordinary  ether  several  times  with 
distilled  water  and  add  solid  caustic  potash  until  most  of  the 
water  has  been  removed.  Then  add  small  pieces  of  clean 
metallic  sodium  until  there  is  no  further  evolution  of  hydrogen 
gas.  The  ether  thus  prepared  should  be  kept  over  metallic 
sodium  and  a  tube  of  calcium  chloride  should  be  inserted  in 
the  stopper,  in  order  to  allow  of  the  escape  of  any  accumulated  gas. 

Potassium  Sulphide. — Dissolve  40  grams  of  the  crystallized 
salt  in  I  liter  of  water  and  filter  through  glass  wool. 

Potassium  Hydroxide  (for  Kjeldahl  process). — Dissolve  700 
grams  of  the  best  quality  of  stick  potash  in  water  and  dilute 
to  I  liter. 

Basic  Lead  Acetate. — Boil  for  half  an  hour  440  grams  of 
lead  acetate  and  264  grams  of  litharge  in  1500  c.c.  of  water. 
Cool  and  dilute  to  2  liters.  Allow  to  settle  and  siphon  off 
the  clear  liquid.  (Sp.  gr.  about  1.27,  containing  about  35 
per  cent,  of  the  basic  salt.) 

Ferric  Alum. — Dissolve  2  grams  of  ferric  alum  in  100  c.c. 
of  water,  boil  the  solution  until  a  precipitate  appears,  and  filter. 

Fehling's  Solution. — (a)  Dissolve  69.28  grams  of  C.P.  crys- 
tallized copper  sulphate,  carefully  dried  between  blotting-paper, 
in  water  and  make  up  to  i  liter,  including  i  c.c.  of  strong  sul- 
phuric acid;  {b)  Dissolve  346  grams  of  sodium  potassium  tar- 
trate and  100  grams  of  sodium  hydroxide  in  water  and  make 
up  to  a  liter. 


BIBLIOGRAPHY. 


The  following  list  comprises  some  of  the  more  important 
works  bearing  on  the  subjects  treated  in  the  preceding 
pages.  A  bibliography  of  the  chemistry  of  foods  com- 
plete to  1882  may  be  found  in  the  Second  Annual  Report 
of  the  New  York  State  Board  of  Health,  and  more  or  less 
complete  bibliographies  are  to  be  found  in  Sadtler's  ''In- 
dustrial Organic  Chemistry,"  Blyth's  ''  Composition  and 
Analysis  of  Foods,"  and  Leach's  "  Food  Inspection  and 
Analysis." 

AIR. 

Air  and  Rain.     R.  Angus  Smith.     Longmans,  Green  &  Co.     London.      1872. 

Air  and  its  Relations  to  Life.     Walter  N.    Hartley.      D.   Appleton  &  Co, 
New  York.      1875. 

Report  on  the  Air  of  Glasgow.     E.   M.    Dixon.     Rol)ert  Anderson.     Glas- 
gow.     1877. 

Recherches  sur  I'Air  Confine.     A.  Braud.     BaiUiere  et  Fils.     Paris.      1880. 

Air  Analysis.     J.    A.    Wanklyn  and   W.   J.    Cooper.     Kegan   Paul,   Trench, 
Triibner  &  Co.     London.      1890. 

Les  Poisons  de  I'Air.     N.  Grehaut.     Bailliere  et  Fils.     Paris.      1890. 

Treatise  on  Hygiene  and  PubHc  Health.     Vol.  I.     Thomas  Stevenson  and 
S.  F.  Murphy.     Blakiston,  Son  &  Co.     Phila.      1892. 

Air  and  Water.     Vivian  B.  Lewes.     Methuen  &  Co.     London.      1892. 

Methods  for  the  Determination  of  Organic  Matter  in  Air.     D.   H.   Bergey. 
Smithsonian  Institution.     Washington,  D.  C.      1896. 

The   Detection  and   Measurement   of   Inflammable   Gas  and  Vapor  in   the 
Air.     Frank  Clowes.     Crosby,  Lockwood  &  Son.     London.     1896. 

Sanitation  in  Daily  Life.     Ellen  H.  Richards.     Whitcomb  &  Barrows. 

Air  Currents  and  the  Laws  of  Ventilation.     W.  W.  Shaw.     Cambridge,  at 
the  University  Press. 

VENTILATION, 

Heating  and  Ventilation  of  the  New  Building,  Mass.   Inst.   Tech.     S.  H. 
Woodbridge.     Tech.  Quart.,  2,  76.      1888. 

263 


^64 


BIBLIOGRArilV. 


Heating  and  Ventilation.     J.  S.   Billings.     Sanitary  En;      eer.     New  York. 

1893. 
Heating  and   Ventilating   Buildings.     Rolla   C.   Carpenter.     John  Wiley  & 

Sons.     New  York.      1895. 

WATER. 

Report  of  the  Royal  Commission  on  \A'ater  Supply.  Great  Britain  Par- 
liamentary Documents.     London.     1 869-' 70. 

Sixth  Report  of  Rivers  Pollution  Commission,  Great  Britain.  London. 
1876. 

Water  Softening  and  Scientific  Filtration.  Walter  George  Atkins.  E.  & 
F.  N.  Spon.     London.      1880. 

National  Board  of  Health  Report  for  1882. 

Water  Supply  (Considered  mainly  from  a  Chemical  and  Sanitary  Standpoint) . 
W.  R.  Nichols.     John  Wiley  &  Sons.     New  York.      1883. 

Water  Analysis  for  Sanitary  Purposes.  E.  Frankland.  John  Van  Voorst. 
London.      1890. 

The  Organic  Analysis  of  Potable  Waters.     J.  A.  Blair.      1890. 

Drinking  Water  and  Ice  SupDlies.  T.  Mitchell  Prudden.  G.  P.  Putnam 
&  Sons.     New  York.      1891. 

Potable  Water.     Floyd  Davis.     Silver,  Burdett  &  Co.     New  York.      1891. 

The  Action  of  Water  on  Lead.  John  Henry  Garrett.  H.  K.  Lewis. 
London.      1891. 

Treatise  on  Hygiene  and  Public  Health.  Vol.  I.  Thomas  Stevenson  and 
S.  F.  Murphy.     Blakiston,  Son  &  Co.     Phila.      1892. 

Sewage  Disposal  in  the  United  States.  Geo.  W.  Rafter  and  M.  N.  Baker. 
D.  Van  Nostrand  Co.     New  York.      1894. 

Les  Eaux-d'Alimentation,  Epuration,  Filtration,  Sterihzation.  Edm. 
Guinochet.     BaiUiere  et  Fils.     Paris.     1894. 

Micro-Organisms  in  Water.  Percy  F.  Frankland  and  Mrs.  Percy  F.  Frank- 
land.     London.      1894. 

The  Filtration  of  Public  Water  Supplies.  Allen  Hazen.  John  Wiley  & 
Sons.     New  York.      1895. 

Examination  of  Water  for  Sanitary  and  Technical  Purposes.  Henry  Leff- 
man.      Blakiston,  Son  &  Co.     Phila.      1895. 

Sev\age  Disposal  on  the  Farm  and  Protection  of  Drinking  Water.  Theo- 
bald Smith.     U.  S.  Dept.  Agr.,  Farmers'  Bull.  43-      1^96. 

Water  Supply  (Considered  Principally  from  a  Sanitary  Standpoint).  W 
P.  Mason.     John  Wiley  &  Sons.     New  York.      1903. 

Water  Analysis.  J.  A.  Wanklyn  and  E.  T.  Chapman.  Tenth  Ed.  Kegan 
Paul,  Trench,  Triibner  &  Co.     London.      1896. 

Examination  of  Water  and  Water  Supplies.  John  C.  Thresh.  H.  A. 
Churchill  &  Co.     London.      1896. 

Mikroskopische  Wasseranalyse.     Carl  Mez.     J.  Springer.     Berlin.      1898. 

A  Simple  Method  of  Water  Analysis.  John  C.  Thresh.  J.  &  A.  Churchill- 
London.     1898. 


BIBLIOGRAPHY.  265 

Water  Purification  at  Louisville,   Ky.     Geo.  W.  Fuller.     D.  Van  Nostrand 

Co.     New  York.      1898. 
Report  on  Water  Purification  at  Cincinnati,   O.     Geo.   W.   Fuller.     Board 

of  Trustees,  Cincinnati.      1899. 
Report  of  Filtration  Commission,   Pittsburgh,  Pa.      1899. 
Examination  of  Water  (Chemical  and  Bacteriological).     William  P.  Mason. 

John  Wiley  &  Sons.     New  York.      1899. 
The    Microscopy   of    Drinking   Water.     Geo.    C.    Whipple.     John    Wiley   & 

Sons.     New  York.     1 899. 
Geological  Survey.     State  of  Washington.      1901, 

Report  of  Streams  Examination,  Sanitary  District  of  Chicago.      1902. 
Chemical  Survey  of  the  Waters  of  Illinois.      1 897-1902. 
Water  and  its  Purification.     S.  Rideal.     Crosby,  Lockwood  &  Son.     London. 

1902. 
Report  on  Water  Purification  Investigations.     New  Orleans  Sewerage  and 

Water  Board.      1903. 
Elements  of  Water  Bacteriology.      S.   C.   Prescott  and  C.-E.  A.   Winslow. 

John  Wiley  &  Sons.     New  York.      1904. 
State  Board  of  Health  Reports  for  Massachusetts,  Michigan,  IlHnois,  Ohio. 

The    Mass.    Reports    for    1872-75    and    1890- 1900,    especially,  contain 

many  valuable  papers,  the  following  being  some  of  the  most  important 

of  them : 
Chemical  Examination  of  Water  and  Interpretation  of  Analyses,     Thomas 

M.  Drown.     Rep.  Mass  State  Board  of  Health,  1892,  319. 
Discussion  of  Special  Topics  Relating  to  the  Quality  of  Public  Water  Sup- 
plies.    F.   P.   Stearns  and  T.   M.   Drown.     Rep.   Mass.   State  Board  of 

Health,  1890,  717. 
On  the  Amount  of   Dissolved  Oxygen  contained  in  Waters  of  Ponds  and 

Reservoirs    at    Difi"erent    Depths.     Thomas    M.     Drown.     Rep.    Mass. 

State  Board  of  Health,  1891,  373. 
On  the  Amount  of  Dissolved  Oxygen  contained  in  Waters  of  Ponds  and 

Reservoirs  at  Different  Depths  in  Winter  under  the  Ice.     Thomas  M. 

Drown.     Rep.  Mass.  State  Board  of  Health,  1892,  333. 
On  th2  Mineral  Contents  of  Some  Natural   Waters  in  Mass.     Thomas  M. 

Drown.     Rep.  Mass.  State  Board  of  Health,  1892,  345. 
The  Efi"ect  of  the  Aeration  of  Natural  Waters.     Thomas  M.  Drown.     Rep. 

Mass.  State  Board  of  Health,  1891,  385. 

In  addition  to  the  above  the  following  papers  contain 
much  information  of  value  on  special  topics  relating  to 
water  supply  and  water  analysis: 

Chemical    Examination    of    Drinking    Water.     Thomas    M.    Drown.     Proc 
Soc.  Arts.,  M.  I.  T.,  1887-8,  87. 


266  BIBLIOGRArHV. 

The     Analysis    of     Water— Chemical,     Microscopical,    and     Bacteriological 

Thomas  M.  Drown.     J.  N.  E.  Water  Works  Assoc,  4  (1889).  79- 
On  the  Loss  on  Ignition  in   Water  Analysis.     Thomas  M.    Drown.      Tech. 

Quart.,  2  (1888),  132. 
The    Odor    and    Color    of    Surface    Waters.     Thomas     M.   Drown.     Tech. 

Quart.,  I  (1888),  250. 
Reduction   of   Nitrates  by   Bacteria.     Ellen   H.  Richards  and   George   W. 

Rolfe.     Tech.  Quart.,  9  (1896),  40. 
The   Purification   of    Water   by   Freezing.     Thomas   M.    Drown.     J.    N.    E. 

Water  Works  Assoc,  8  (1893),  46. 
The  Filtration  of  Natural  Waters.     Thomas  M.   Drown.     J-   of  the  Assoc. 

of  Eng.  Soc,  9  (1890),  356. 
A  Study  of  Self-Purification  in  the  Sudbury  River.         A.   G.   Woodman, 

C.-E.  A.  Winslow,  and  P.  Hansen.     Tech.  Quart.,  15,  1902. 
Normal  Distribution  of  Chlorine  in  Connecticut.     H.   E.   Smith  and  F.  S. 

HolUs.     Rept.  Conn.  State  B'd  Health,  1902. 
Water  Supplies  of  S.   E.   Alaska  and  the  Black  Hills  of    S.   Dak.      E.  H. 

Richards.     Tech.  Quart.,  16,  1903. 
Notes  on  the   Potable   Waters  of  Mexico.     E.    H.    Richards.     Trans.   Am. 

Inst.  Min.  Eng.,  1901. 
Rainfall  on  the  Pacific  Coast  and  the  Factors  of  Water  Supply  in  Cahfornia. 

J,  Assoc.  Eng.  Soc,  1903. 


WATER. 

Department  of  Interior.     U.  S.  Geological  Survey.     Underground  Water:    Water 
Supply  and  Irrigation  Paper.     No.  i6c.     Myron  L.  Fuller. 
Field  Assay  of  Water.     No.  151.     Marshall  O.  Leighton. 

Value  of  Pure  Water.  George  C.  Whipple.  Published  by  John  Wiley  &  Sons. 
New  York. 

Report  of  the  Commission  on  Additional  Water  Supply  for  the  City  of  New  York. 
Appendix  VI. 

Report  of  the  Committee  on  Standard  Methods  of  Water  Analysis  to  the  Labora- 
tory Section  of  the  American  Public  Health  Association.  (Reprinted  from 
the  Journal  of  Infectious  Diseases,  Supplement  No.  i.     May,  1905.) 

Disposal  of  Dairy  and  Farm  Sewage  and  Water  Supply.  Oscar  Erf.  Kansas 
State  Agricuhural  College  Experiment  Station  Bulletin. 


BIBLIOGRAPHY.  267 

FOOD. 

The  list  given  here  is  Hmited  to  books  published  since 
1890. 

Traite     General     d'Analyse     des     Beurres.     A.     J.     Zune.     H.     Lamartin. 

Paris.      1892. 
Die  Menschlichen  Nahrungs-  u.  Genussmittel.     J.    Konig.     Julius  Springer. 

Berlin.      1893. 
Foods   and    Dietaries.       R.    W.    Burnet,    M.D.       P.    Blakiston,     Son    &    Co. 

Phila.      1 893. 
Analyse    des   Matieres   Alimentaires   et    Recherche    de    Leur    Falsifications. 

Ch.  Girard  et  A.  Dupre.     Vve.  Ch.  Dunod  &  P.  Vicq.     Paris.      1894. 
Animal  and  Vegetable  Oils,  Fats,  Butters  and  Waxes.     C.  R.  Alder  Wright. 

Griffin  &  Co.     London.      1894. 
Chemistry  of   Wheat,    Flour,   and   Bread.     Wm.   Jago.     Simpkin   Marshall, 

London.      1895. 
The  Food  Products  of  the  World.     Dr.  Mary  H.  Green.     The  Hotel  World 

Chicago.      1895. 
The   Story   of   Germ    Life.     H.    W.    Conn.     Appleton   &    Co.     New    York 

1897. 
The  Relation  of  Food  to  Health.     George  H.  Townshend.     Witt  Publish 

ingCo.     St.  Louis.      1897. 
The  Analysis  of  Food  and   Drugs.     Part  I:    Milk  and  Milk  Products.     T, 

H.    Pearmain   and    C.    G.    Moor.     Bailliere     Tindall   &    Cox.     London 

1897. 
Principles  and  Practice  of  Agricultural  Analysis.    Harvey  W.  Wiley.    Chem 

Pub.  Co.     Easton,  Pa.      1897. 
Testing  Milk  and  its  Prod-.ctG.     E.  H.  Farrington  and  F.  W.  Woll.     Men 

dota  Book  Co.     Madison,  Wis.      1898. 
Chemical    Analysis    of    Oils,    Fats,    and    Waxes.     J.    Lewkowitsch.      Mac 

millan  &  Co.     London.      1908. 
Commercial  Organic  Analysis.     A.  H.  Allen.     Third  Ed.   Rev.  by  H.  Leff- 

man.      Blakiston,  Son  &  Co.     Phila.      1898. 
Die     Untersuchung    landwirtschaftlich    und     gewerblich    wichtiger    StolTe. 

J.  Konig.     Paul  Parey.     Berlin.      189S. 
Food    Materials    and    their    Adulterations.     Ellen     H.     Richards.     Home 

Science  Pub.  Co.     Boston.      1908. 
Plain    Words    about    Food.     The    Rumford    Kitchen    Leaflets.     Ellen    H. 

Richards,  Ed.     Home  Science  Pub.  Co.     Boston.      1899. 
Muscle,  Brain,  and  Diet :   A  Plea  for  Simpler  Foods.     E.  H.  Miles.     Sonnen- 

schien.     London.      1900. 
A    Handbook    of    Industrial     Organic    Chemistry.     S.     P.     Sadtler.     J.   B. 

Lippincott  Co.     Phila.      1900. 
Flesh  Foods  with  Methods  for  their  Chemical,   Microscopical,   and  Bacte- 
riological    Examination.     C.     A.     Mitchell.     Griffin     &     Co.     London. 

1900. 


268  BIBLIOGRAPHY. 

Food  and  the  Principles  of  Dietetics.     R.  Hutchinson.     Wood.     New  York. 

1 901. 
The  Cost  of  Food:    A  Study  in  Dietaries.     E.   H.   Richards.     J.   Wiley  & 

Sons.     New  York.      1901. 
Select  Methods  in  Food  Analysis.     H.  Leffman  and  W.  Beam.     P.  Blakis- 

ton's  Son  &  Co.     Phila.      1905. 
Suggested  Standards  for  Food  and  Drugs.     C.  G.  Moor.     BailHere,  Tindall 

&  Cox.     London.      1902. 
En23rmes   and   their   Applications.     J.    Effront.     Trans.  S.  C.  Prescott.     J. 

Wiley  &  Sons.     New  York.      1902. 
Foods:    their  Composition  and  Analysis.     A.  W.  Blyth  and  M.  W.  Blyth. 

Griffin  &  Co.     London.      1903. 
Food  Inspection  and  Analysis.    Albert  E.  Leach.     Wiley  &  Sons.     New 

York.     1904. 
Organic  Analysis.      Henry  C.   Sherman.      Macmillan  Co.      New   York. 

1505. 
Foods  and  their  Adulteration.     H.  W.  Wiley.     P.  Blackiston's  Son  &  Co. 

Phila.     1907. 


The  following  bulletins  of  the  United  States  Depart- 
ment of  Agriculture  will  also  be  found  useful  for  study  or 
reference  on  the  general  question  of  food: 

Office  of  Experiment  Stations,  Bulletins. 

No.    9.  Fermentations  of  Milk.      1892. 

II.  Analyses  of  American  Feeding  Stuffs.      1892. 

21.  Chemistry  and  Economy  of  Food.     1895. 
No.  25.  Dairy  Bacteriology.      1895. 

28.  (Rev.    Ed.)    Chemical    Composition    of    American    Food   MaterialsL 

1895. 

29.  Dietary  Studies  at  the  University  of  Tennessee.     1896. 

31.  "  "         "     "  "  "  Missouri.      1896. 

32.  "  "         "  Purdue    University.      1896. 

34.  Carbohydrates  of  Wheat,  Maize,  Flour,  and  Bread.      1896. 

35.  Food  and  Nutrition  Investigations  in  New  Jersey.      1896. 

37.  Dietary  Studies  at  the  Maine  State  College.      1897. 

38.  "  "        — Food  of  the  Negro  in  Alabama.      1897. 
40.         "  "        in  New  Mexico.      1897. 

43.  Composition  and  DigestibiUty  of  Potatoes  and  Eggs.      1897. 

44.  Metabolism  of  Nitrogen  and  Carbon  in  the  Human  Organism.     1897. 


BIBLIOGRAPHY.  269 

45.  A  Digest  of  Metabolism  Experiments.      1897. 

46.  Dietary  Studies  in  New  York  City.      1898. 

52.  Nutrition  Investigations  in  Pittsburgh,  Pa.      1898. 

53.  "  "  at  the  University  of  Tennessee.      1898. 

54.  "  "  in  New  Mexico.      1898. 

55.  Dietary  Studies  in  Chicago.     1898. 

63.  Experiments  on  the  Conservation  of  Energy  in  the  Human  Body, 
1899. 

66.  Creatin  and  Creatinin.      1899. 

67.  Bread  and  Bread  Making.      1899. 

69.  Experiments  on  the  Metabohsm  of  Matter  and  Energy  in  the  Human 
Body.      1899. 

71.  Dietary  Studies  of  Negroes.      1899. 

75.         "  "        "  University  Boat  Crews.      1900. 

84.  Nutrition  Investigations  at  the  CaHfornia  Agr.  Expt,  Station.      1900. 

85.  Investigations  on  the   DigestibiHty  and  Nutritive  Value  of  Bread. 

1900. 
89.  Effect  of  Muscular  Work  on  Digestion  of  Food  and  Metabolism  of 

Nitrogen.      1901. 
91.  Nutrition  Investigations  at  the  University  of  Illinois,  etc.      1901. 
98.  Effect  of  Severe  and  Prolonged  Muscular  Work  on  Food  Consump- 
tion, Digestibility,  and  Metabolism.      1901. 
loi.  Studies  on  Bread  and  Bread  Making.      1901. 
102.   Losses  in  Cooking  Meat.      1901. 

107.  Nutrition  Investigations  among  Fruitarians  and  Chinese.     1901. 
109.  Metabolism  of  Matter  and  Energy  in  the  Human  Body.      1902. 

116.  Dietary  Studies  in  New  York  City.      1902. 

117.  Effect    of    Muscular  Work  upon    Digestibility  of    Food  and  Metab- 

olism of  Nitrogen.      1902. 
121.  Metabolism    of    Nitrogen,  Sulphur,  and    Phosphorus  in  the  Human 

Organism.      1902. 
126.  Digestibility  and  Nutritive  Value  of  Bread.      1903. 
129.  Dietary  Studies :   Boston  and  other  Places.      1903. 
132.  Further  Investigations  among  Fruitarians.     1903. 

Division  of  Chemistry,  Bulletins. 

No.  13.  Foods  and  Food  Adulteration — (Ten  Parts).     1887-1902. 

45.  Analyses  of  Cereals.      1895. 

46.  Official  Methods  of  Analysis.      1895. 
50.  Composition  of  Maize.      1898. 

59.  Composition  of  American  Wines.      1900. 

61.  Pure  Food  Laws  of  Foreign  Countries.      1901. 

65.  Provisional  Methods  for  Analysis  of  Foods.     1902. 

66.  Fruits  and  Fruit  Products.      1902. 
69.  Foods  and  Food  Control.     1902. 

72.  American  Wines  at  Paris  Exposition  of  1900.     1903, 


270  .  BIBLIOGR  VPHY. 


Farmers'  Bulletins. 

No,  23.  Foods:  Nutritive  Value  and  Cost.      1894, 

29.  Souring  of  Milk.      1895. 

34.  Meats:  Composition  and  Cooking.      1896. 

74.  Milk  as  Food.      1898. 

^S-  Fish  as  Food.      1898. 

'';3.  Sugar  as  Food.      1899, 

112.  Bread  and  the  Principles  of  Bread  Making.      1900. 
121.  Beans,  Peas,  and  other  Legumes  as  Food.      1900. 
128.  Eggs  and  their  Uses  as  Food.      1901. 
131.  Household  Tests  for   Detection  of   Oleomargarine  and  Renovated 

Butter.      1 90 1. 
142.  The  Nutritive  and  Economic  Value  of  Food      1901. 

Bureau  of  Chemistry  Bulletins. 
No.  77.  Olive  Oil  and  Its  Substitutes. 

84.  I  fluence  of  Food   Preservatives  and  Artificial  Colors  on  Digestion  and 

Health. 
100.  Some  Forms  of  Food  Adulteration  and  Simple  Methods  for  their  Detection. 
107.  Official  and  Provisional  Methods  of  Analvsis. 
no.  Chemical  Analysis  and  Composition  of  American  Honeys. 
114.  Meat  Extracts  and  Similar  Preparations. 

Much  valuable  information  will  also  be  found  in  the  monthly  bulletins  and 
reports  of  several  of  the  State  experiment  stations  and  boards  of  health,  notably 
those  of  Connecticut,  North  Dakota,  Maine,  Kansas,  New  Hampshire,  Vermont, 
and  Massachusetts. 


INDEX. 


PAGE 

Acceptable  water 80 

Acid  hydrolysis,  of  starch 211 

mercuric  nitrate,  preparation  of 260 

,  sulphanilic,  reagent  for  nitrite  test 2:^7 


,  sulphuric,  reagent  for  air  analysis. 


3D 


,  "■         ,  free  from  nitrogen 258 

Acids,  determination  in  wine 220 

,  volatile,  in  wine 220 

Adams'  method  for  fat  determination 1 7  r 

Adulteration,  cause  of 1^6 

defined 156 

,  extent  of 160 

Air,  amount  required  per  capita 20 

currents,  location  of 25 

,  composition  of  expired 10 

,  ' '  inspired 10 

,  dust  in 18 

,  effect  of  humidity  in 14 

essential  to  life 3 

,  occasional  impurities  in 16,  17 

of  cities 17 

,  variations  in  composition  of 12 

,  water  vapor  in 14 

Albumin,  determination  in  milk 184 

Albuminoid  ammonia,  in  relation  to  organic  nitrogen 108 

in  water,  determination  of 100 

Alcohol,  determination  in  lemon  extract 232 

,  "  "  wine 217 

,  table  for  determining 244 

-extract  ratio : 218 

Alkalinity  in  water 119 

Alkaline  permanganate,  reagent  for  water  analysis 256 

Aluminum  hydroxide 259 

271 


272 


INDEX. 


PAGE 

Alum  in  water,  determination  of 137 

Alumina,  milk  of,  reagent 259 

Ammonia,  standard  solution,  preparation  of 257 

,  presence  in  water 78 

,  in  water,  determination  of 100 

Analyses,  interpretation  of 82 

Aqueous  vapor,  tension  of 236 

Ash,  determination  in  cereals 206 

,  in  wine 218 

,  of  milk 1 73 


Babcock  method  for  fat  determination 176 

Barium  hydroxide,  reagent  for  air  analysis 255 

Beer,  analysis  of 224 

Benzoic  acid,  detection  of 223 

Bibliography 263 

Biological  examination  of  water 135 

Boric  acid,  detection  in  milk 188 

Breakfast  foods j6i 

Brook  water 86 

Butter,  analysis  of 193 

,  complete  analysis  of 204 

,  composition  of 191 

Calcium  chloride,  standard  solution  of 259 

Calorie,  definition  of •. 148 

Cane-sugar,  detection  in  milk 185 

Caramel,  detection  in  vanilla 230 

Carbohydrates,  function  of 1 46 

,  separation  in  cereals 209 

Carbon  dioxide,  amount  expired 15 

,  determination  of,  in  air 27 

,  "popular  tests"  for 40 

as  a  disturbing  factor 12 

,  properties  of 21 

table  of  weight  of  cubic  centimeter  of 237 

in  water,  determination  of 1 29 

,  a  test  of  ventilation 23 

Carbonaceous  matter  in  water,  determination  of ii 2 

Carbonic  acid  in  water,  determination  of  free 129 

Carbon  monoxide,  detection  of,  in  air 49 

,  estimation  of,  in  air 50 

,  effect  on  blood 16 

Change  on  ignition 117 


INDEX. 


27J 


PAGB 

Chlorine  in  ground  water qq, 

water,  determination jj^ 

<(                       f                                                                           -^ 

,  source  oi ^  j 

Casein,  determination  of , jg . 

Citral,  determination  of 27? 

Clark's  method  for  hardness j  j  -. 

Classification  of  waters g~. 

Cocoanut  oil,  detection  in  butter jq^ 

Cohen  method  for  carbon  dioxide ^g; 

Collection  of  water  samples q^ 

Color  of  water,  determination  of j  -,q, 

standards  for  water i^o-i  ?^ 

Colors,  detection  of 221 

in  milk ig5. 

in  food 16^ 

Condensed  milk,  analysis  of jgp, 

,  composition  of jgq 

Cooking,  changes  caused  by j^g 

Coumarin,  determination  of 227 

,  Leach's  test  for 228 

Cream,  determination  of j  ^ j 

"  Crowd  poison  " 18-24 

Crude  fibre,  determination  of 214 

Cycle  of  nitrogen _  ,  51- 

Dextrin,  estimation  in  cereals 2iO' 

Diastase,  estimation  of  starch  by 212 

Dietaries j  r  2 

Dissolved  oxygen,  reagents  for,  preparation  of 260 


in  water,  determination  of i 


23 


Distilled  water y^ 

Dust  and  soot 54^  c  r^  r^ 

,  estimation  of,  in  air r^^ 


Ether,  anhydrous,  preparation  of 261 

extract  of  cereals 206 

Extract  in  beer-wort,  table  for 240 

,  determination  in  beer , 224 

,             "              "  wine 217 

in  wine,  table  of 247 

Fat,  determination  of,  in  milk 171- 

Fats,  value  of 14c 

Fatty  acids,  determination  of,  in  butter ig5 


274  INDEX. 

PAGE 

Fehling's  solution,  preparation  of 261 

Filters 87 

Fitz  and  Wolpert 43 

method  for  carbon  dioxide 45 

shaker 45~47 

Fluorides,  detection  of 226 

Food,  composition  of 1 43 

,  definition  and  uses 1 43 

,  principles 1 43 

,  materials,  table  of  composition  of 150 

,  predigested 162 

Formaldehyde,  detection  in  milk 187 


G  lass  pipe 94 

Glycerine,  determination  in  wine 219 

Gottlieb  method  for  fat  estimation 1 78 

Ground  water,  history  of 62 

Gunning  method  for  nitrogen 209 


Hanus'  iodine  solution,  preparation  of 260 

Hardness  in  water,  determination  of 117 

,  table  of 242 

Heat  of  combustion,  values  for 148 

Humidity  in  air,  effect  of 14 


Ice,  rules  for  use  of 72 

Interpretation  of  water  analysis 82 

Iodine  value,  determination  of 197 

Iron  in  water,  determination  of 127 

,  standard  solution  of 259 


Kjeldahl  method  for  nitrogen 206 


Lactose,  estimation  of 181 

Lake  water 84 

Lead  acetate,  basic,  preparation  of 261 

in  water,  determination  of 139 

,  standard  solution  of 260 

Lemon  extract 23 1 

oil,  determination  of 23  2 

Lime  water,  reagent  for  air  analysis 255 

Loss  on  ignition  in  water,  determination  of 115 


INDEX. 


275 


PAGE 

IMalt  extract,  preparation  of 213 

Melting  point  of  butter    2or 

Meteoric  water ^g 


Micro-organisms,  estimation  of  in  air 


51 


,  role  of,  in  water 65 

Milk,  acidity  of 172 

,  adulterations  of 184 

,  composition  of 1 68 

,  fermentations  of 1 69 

,  reaction  of 172 

,  relation  of  constituents 179 

,  United  States  standard .• 169 

sugar,  estimation  of i8r 

Mineral  salts,  value  in  food 147 

substances  in  water 91 

Misbranding,  defined 157 

Mountain  "  sickness  " 13 

Nutritive  ratio 1 49 

Nitrates  in  ground  water 91 

in  water,  determination  of no 

Nitrate  standard  solution,  preparation  of 258 

Nitrogen,  cycle  of 65 

,  determinaiion  of,  by  Kjeldahl  method 106 

essential  to  living  matter 75 

,  total  organic,  determination  of,  in  water 106 

Nitrogenous  substances,  function  of 144 

Nitrites  in  w^ater,  determination  of 108 

estimation  of,  in  air 51 

Nitrite  standard  solution,  preparation  of 257 

Naphthylamine  acetate  reagent  for  nitrite  test 257 

Nessler's  reagent,  preparation  of 256 

Odor  of  water,  detection  of 133 

,  analytical  value  of 88 

Oleomargarine 192 

Opacity  of  milk 171 

Organic  matter  in  the  air 52 

nitrogen  in  water,  determination  of 106 

"  Oxygen  consumed,"  determination  of 112 

Oxygen  dissolved  in  water,  determination  of 1 23-1 29 

table  for 242 

Pentosans,  determination  of 213 

Pettenkofer  method  for  carbon  dioxide 28 


276 


INDEX. 


PAGE 

Petterson  and  Palmquist  apparatus 40 

Phosphates  in  water,  determination  of 120 

Purified  vs.  clarified  water 69 

"  Popular  tests  "  for  carbon  dioxide 70 

Potassium  chromate,  reagent,  preparation  of 259 

ferrocyanide 61 

hydroxide 258 

iodide  reagent, 261 

sulphide  reagent 262 

sulphocyanide  reagent 259 

Pressure,  influence  on  respiratory  exchange 13 

Preservatives  in  food 163 

Proteids  of  milk,  determination  of 183 

,  Kjeldahl  method  for 206 

Residue  on  evaporation,  determination  of 115 

Reducing  sugar,  determination  in  beer 225 

Reducing  sugar,  Munson  and  Walker's  table  for 248 

Refractive  index  of  butter 201 

Refractometer,  Abbe 202 

Reichert-Meissl  number 194 

Renovated  butter 192 

,  detection  of 200 

Resins,  detection  in  vanilla 229 

Respiratory  exchange 15 

quotient 14 

River  water 85 

"Safe"  water 75-79 

Salicylic  acid,  detection  of 223 

Salt,  determination  in  butter 204 

Samples,  collection  of  water 96 

Sanitary  chemistry,  scope  of i 

science,  importance  of 2 

Sediment  of  water,  estimation  of 13^ 

"Sewer-air" i7~24 

Shallow  wells 9° 

Silver  nitrate,  chlorine  reagent 259 

Soap,  standard  solution  of 259 

Sodium  carbonate,  detection  in  milk 188 

chloride,  standard  solution 258 

Solids  of  milk 1 73 

Soot,  estimation  of,  in  air - 54 

Specific  gravity  of  butter 201 

milk 1 70 


INDEX. 


277 


PAGB 


Specific  gravity  of  milk,  table  for 243 

wine 216 

Spoon  test I  gg 

Springs 88 

Starch,  detection  in  milk 186 

,  determination  of 211 

Steam  vacuum 50,  51 

Storage  of  water 71,  87 

Sugars,  determination  in  cereals 210 

Sulphites,  detection  of 225 

Surface  water 85,  89 

,  character  of 72 

Turbidity  of  v^-ater,  estimation  of 136 

Turmeric,  detection  of 233 

Vanilla  extract 226 

Vanillin,  determination  of 227 

Ventilation,  apparatus  to  illustrate 24 

,  natural  vs.  artificial 23 

a  necessity 19 

,  principle  of 22 

,  requirements  of 26 

,  to  test  efficiency  of 24 

Vital  capacity 10 

Walker  method  for  carbon  dioxide 34 

Water,  acceptable 82 

Water  analysis,  blank  form  for 141 

,  points  to  determine  in 80 

,  statement  of  results 140 

,  value  of 94 

Water,  classification  of 85 

,  circulation  of 6r 

,  determination  in  butter 204 

,  illustration  of  contamination  of 62 

,  its  relation  to  health 66 

,  legal  restrictions  upon  use  of 57 

,  need  of 6 

,  passage  through  the  ground 64 

,  preliminary  inspection  of  source  of 80 

,  presence  of  organisms  in 66 

,  solvent  power  of 65 

,  storage  of 71 

,  the  ideal  drinking-water 59 


-'/- 


INDEX. 


PAGE 

Water- vapor  in  air i6 

Water  siphon 48,  49 

,  daily  quantity  needed 6 

Water-pipes 94 

Waters,  table  of  average  composition  of 238 

normal i  .^y 

,  polluted,  table  of 240,  241 

Water  free  from  ammonia,  preparation  (;f 255 

,  determination  in  cereals 205 

"   milk 185 

Well-water 90 

Wine,  analysis  of 216 

,  composition  of 215 

Wolpert  shaker 47 

Wooden  pipe 94 


Short-title  Catalogue 

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*  Lorenz's  Modem  Refrigerating  Machinery.   (Pope,  Haven,  and  Dean)..8vo,  4  00 
MacCord's  Kinematics;  or.  Practical  Mechanism 8vo,  5  00 

Mechanical  Drawing 4to,  4  00 

Velocity  Diagrams 8vo,  1  50 

MacFarland's  Standard  Reduction  Factors  for  Gases .8vo,  1  50 

Mahan's  Industrial  Drawing.      (Thompson.) 8vo,  3  50 

Mehrtens's  Gas  Engine  Theory  and  Design Large  12mo,  2  50 

Oberg's  Handbook  of  Small  Tools Large  12mo,  3  00 

*  Parshall  and  Hobart's  Electric  Machine  Design.  Small  4to,  half  leather,  12  50 

Peele's  Compressed  Air  Plant  for  Mines 8vo,  3  00 

Poole's  Calorific  Power  of  Fuels 8vo,  3  00 

*  Porter's  Engineering  Reminiscences,  1855  to  1882 8vo,  3  00 

Reid's  Course  in  Mechanical  Drawing 8vo,  2  00 

Text-book  of  Mechanical  Drawing  and  Elementary  Machine  Design.Svo,  3  00 

13 


Richards's   Compressed  Air 12mo,  $1   50 

Robinson's  Principles  of  Mechanism 8vo,  3  00 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  00 

Smith  (A.  W.)  and  Marx's  Machine  Design 8vo,  3  00 

Smith's  (O.)  Press- working  of  Metals Svo,  3  00 

Sorel's  Carbureting  and  Combustion  in  Alcohol  Engines.      (Woodward  and 

Preston.) Large  12mo,  3  00 

Stone's  Practical  Testing  of  Gas  and  Gas  Meters Svo,  3  50 

Thurston's  Animal  as  a  Machine  and  Prime  Motor,  and  the  Laws  of  Energetics. 

12mo,  1  00 

Treatise  on  Friction  and  Lost  Work  in  Machinery  and  Mill  Work.  .  .Svo,  3  00 

*  Tillson's  Complete  Automobile  Instructor 16mo,  1   50 

*  Titsworth's  Elements  of  Mechanical  Drawing Oblong  Svo,  1  25 

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*  Waterbury's  Vest  Pocket  Hand-book  of  Mathematics  for  Engineers. 

2iX5|  inches,  mor.  1  00 

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Weisbach's    Kinematics    and    the   Power   of    Transmission.      (Herrmann — • 

Klein.) 8vo,  5  00 

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Wood's  Turbines Svo,  2  50 


MATERIALS   OF  ENGINEERING. 

*  Bovey's  Strength  of  Materials  and  Theory  of  Structures Svo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering Svo,  7  50 

Church's  Mechanics  of  Engineering Svo,  6  00 

*  Greene's  Structural  Mechanics Svo,  2  50 

*  HoUey's  Lead  and  Zinc  Pigments Large  12mo  3  00 

HoUey  and  Ladd's  Analysis  of  Mixed  Paints,  Color  Pigments,  and  Varnishes. 

Large  12mo,  2  50 
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Steels,  Steel-Making  Alloys  and  Graphite Large  12mo,  3  00 

Johnson's  (J.  B.)  Materials  of  Construction Svo,  6  00 

Keep's  Cast  Iron Svo,  2  50 

Lanza's  Applied  Mechanics Svo,  7  50 

Maire's  Modem  Pigments  and  their  Vehicles 12mo,  2  00 

Maurer's  Technical  Mechanics Svo,  4  00 

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*  Strength  of  Materials 12mo,  1  00 

Metcalf 's  Steel.     A  Manual  for  Steel-users 12mo,  2  00 

Sabin's  Industrial  and  Artistic  Technology  of  Paint  and  Varnish Svo,  3  00 

Smith's  ((A.  W.)  Materials  of  Machines 12mo,  1  00 

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Thurston's  Materials  of  Engineering 3  vols.,  Svo,  8  00 

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Part  II.     Iron  and  Steel Svo,  3  50 

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Constituents Svo,  2  50 

Wood's  (De  V.)  Elements  of  Analytical  Mechanics Svo,  3  00 

Treatise  on    the    Resistance    of    Materials    and    an    Appendix    on    the 

Preservation  of  Timber Svo,  2  00 

Wood's  (M.  P.)  Rustless  Coatings:    Corrosion  and  Electrolysis  of  Iron  and 

Steel Svo,  4  00 


STEAM-ENGINES   AND   BOILERS. 

Berry's  Temperatiire-entropy  Diagram 12mo,     2  00 

Carnot's  Reflections  on  the  Motive  Power  of  Heat.      (Thurston.) 12mo,      1   50 

Chase's  Art  of  Pattern  Making 12mo,     2  50 

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Dawson's  "Engineering"  and  Electric  Traction  Pocket-book.  ..  .  16mo,  mor. 

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Goss's  Locomotive  Performance 8vo, 

Hemenway's  Indicator  Practice  and  Steam-engine  Economy 12mo, 

Hutton's  Heat  and  Heat-engines 8vo, 

Mechanical  Engineering  of  Power  Plants 8vo, 

Kent's  Steam  boiler  Economy 8vo, 

Kneass's  Practice  and  Theory  of  tiie  Injector 8vo, 

MacCord's  Slide-valves 8vo, 

Meyer's  Modem  Locomotive  Construction 4 to, 

Moyer's  Steam  Turbine 8vo, 

Peabody's  Manual  of  the  Steam-engine  Indicator 12mo, 

Tables  of  the  Properties  of  Steam  and  Other  Vapors  and  Temperature- 
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Valve-gears  for  Steam-engines 8vo, 

Peabody  and  Miller's  Steam-boilers 8vo, 

Pupin's  Thermodynamics  of  Reversible  Cycles  in  Gases  and  Saturated  Vapors. 

(Osterberg.) 12mo, 

Reagan's  Locomotives :  Simple,  Compound,  and  Electric.     New  Edition. 

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Smart's  Handbook  of  Engineering  Laboratory  Practice 12mo, 

Snow's  Steam-boiler  Practice 8vo, 

Spangler's  Notes  on  Thermodynamics 12mo, 

Valve-gears 8vo, 

Spangler,  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo, 

Thomas's  Steam-turbines 8vo, 

Thurston's  Handbook  of  Engine  and  Boiler  Trials,  and  the  Use  of  the  Indi- 
cator and  the  Prony  Brake 8vo, 

Handy  Tables 8vo, 

Manual  of  Steam-boilers,  their  Designs,  Construction,  and  Operation  8vo, 

Manual  of  the  Steam-engine 2  vols.,   8vo, 

Part  I.      History,  Structure,  and  Theory 8vo, 

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Wehrenfennig's  Analysis  and  Softening  of  Boiler  Feed-water.     (Patterson.) 

8vo, 

Weisbach's  Heat,  Steam,  and  Steam-engines.      (Du  Bois.) 8vo, 

Whitham's  Steam-engine  Design 8vo, 

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MECHANICS    PURE   AND    APPLIED. 

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Dana's  Text-book  of  Elementary  Mechanics  for  Colleges  and  Schools  .12mo, 
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Mechanics  of  Engineering.     Vol.     I Small  4to, 

Vol.  II Small  4to, 

*  Greene's  Structural  Mechanics 8vo, 

Hartmann's  Elementary  Mechanics  for  Engineering  Students.      (In  Press.) 
James's  Kinematics  of  a  Point  and  the  Rational  Mechanics  of  a  Particle. 

Large  12mo, 

*  Johnson's  (W.  W.)  Theoretical  Mechanics 12mo, 

Lanza's  Applied  Mechanics 8vo, 

*  Martin's  Text  Book  on  Mechanics,  Vol.  I,  Statics 12mo, 

*  Vol.  II,  Kinematics  and  Kinetics.  12mo, 
Maurer's  Technical  Mechanics 8vo, 

*  Merriman's  Elements  of  Mechanics 12mo, 

Mechanics  of  Materials 8vo, 

*  Michie's  Elements  of  Analytical  Mechanics 8vo, 

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Robinson's  Principles  of  Mechanism 8vo,  $3  00 

Sanborn's  Mechanics  Problems Large  12mo,  1   50 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  00 

Wood's  Elements  of  Analytical  Mechanics 8vo,  3   00 

Principles  of  Elementary  Mechanics 12mo,  1   25 


MEDICAL. 

*  Abderhalden's  Physiological   Chemistry   in   Thirty   Lectures.      (Hall    and 

Def  ren. ) 8vo, 

von  Behring's  Suppression  of  Tuberculosis.      (Bolduan.) 12mo, 

Bolduan's  Immune  Sera 12mo, 

Bordet's  Studies  in  Immunity.      (Gay.) 8vo, 

Chapin's  The  Sources  and  Modes  of  Infection.      (In  Press.) 
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Ehrlich's  Collected  Studies  on  Immunity.      (Bolduan.) 8vo, 

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de  Fursac's  Manual  of  Psychiatry.      (Rosanoff  and  Collins.)..  .  .Large  12mo, 

Hammarsten's  Text-book  on  Physiological  Chemistry.      (Mandel.) 8vo, 

Jackson's  Directions  for  Laboratory  Work  in  Physiological  Chemistry .  .8vo, 

Lassar-Cohn's  Practical  Urinary  Analysis.      (Lorenz.) 12mo, 

Mandel's  Hand-book  for  the  Bio-Chemical  Laboratory 12mo. 

*  Nelson's  Analysis  of  Drugs  and  Medicines 12mo. 

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Rostoski's  Serum  Diagnosis.      (Bolduan.) 12nio, 

Ruddiman's  IncompatibiUties  in  Prescriptions 8vo, 

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Salkowski's  Physiological  and  Pathological  Chemistry.      (Omdorff.)  ..  .  .8vo, 

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Smith's  Lecture  Notes  on  Chemistry  for  Dental  Students 8vo, 

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METALLURGY. 

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in  the  Practice  of  Moulding 12mo, 

Iron  Founder 12mo, 

Supplement 12mo, 

Douglas's  Untechnical  Addresses  on  Technical  Subjects 12mo, 

Goesel's  Minerals  and  Metals:  A  Reference  Book 16mo,  mor. 

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Johnson's    Rapid    Methods   for    the   Chemical    Analysis    of    Special    Steels, 

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Keep's  Cast  Iron 8vo, 

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Minet's  Production  of  Aluminum  and  its  Industrial  Use.      (Waldo.).  .  12mo, 

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Smith's  Materials  of  Machines 12mo, 

Tate  and  Stone's  Foundry  Practice 12mo, 

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page  9. 

Part  II.    Iron  and  Steel 8vo,     3  50 

Part  III.  A  Treatise  on  Brasses,   Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,     2  50 

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Ulke's  Modern  Electrolytic  Copper  Refining 8vo,   S3  00' 

West's  American  Foundry  Practice 12mo,      1   od- 

Moulders'  Text  Book 12mo.     2  50 


MINERALOGY. 

Baskerville's  Chemical  Elements.      (In  Preparation.) 

*  Browning's  Introduction  to  the  Rarer  Elements 8vo, 

Brush's  Manual  of  Determinative  Mineralogy.      (Penfield.) 8vo, 

Butler's  Pocket  Hand-book  of  Minerals 16mo,  mor. 

Chester's  Catalogue  of  Minerals 8vo,  paper, 

Cloth, 

*■  Crane's  Gold  and  Silver 8vo, 

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Large  8vo, 

Manual  of  Mineralogy  and  Petrography 12mo, 

Minerals  and  How  to  Study  Them 12mo, 

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Text-book  of  Mineralogy- 8vo, 

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Eakle's  Mineral  Tables 8vo, 

Eckel's  Stone  and  Clay  Products  Used  in  Engineering.      (In  Preparation.) 

Goesel's  Minerals  and  Metals:  A  Reference  Book 16mo,  mor.      3  00 

Groth's  The  Optical  Properties  of  Crystals.      (Jackson.)      (In  Press.) 

Groth's  Introduction  to  Chemical  Crystallography  (Marshall).  ......  .  12mo,      1   25 

*  Hayes's  Handbook  for  Field  Geologists 16mo,  mor. 

Iddings's  Igneous  Rocks 8vo, 

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With  Thumb  Index 

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pipe  12mo, 

Merrill's  Non-metallic  Minerals:  Their  Occurrence  and  Uses 8vo, 

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8vo,  paper, 

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States 8vo, 

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Eissler's  Modem  High  Explosives 8vo,  4  00 

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Ihlseng's  Manual  of  Mining 8vo,  5  00 

*  Iles's  Lead  Smelting 12mo,  2  50 

Peele's  Compressed  Air  Plant  for  Mines 8vo.  3  00 

Riemer's  Shaft  Sinking  Under  Diflfictilt  Conditions.      (Coming  and  Peele.)8vo,  3  00 

*  Weaver's  Military  Explosives 8vo,  3  00 

Wilson's  Hydraulic  and  Placer  Mining.     2d  edition,  rewritten 12mo,  2  50 

Treatise  on  Practical  and  Theoretical  Mine  Ventilation 12mo,  1  25- 

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SANITARY    SCIENCE. 

Association  of  State  and  National  Food  and  Dairy  Departments,  Hartford 

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Jamestown  Meeting,  1907 8vo,  3  00 

*  Bashore's  Outlines  of  Practical  Sanitation ]2mo,  1   25 

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Chapin's  The  Sources  and  Modes  of  Infection.      (In  Pres,.) 

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Water-supply  Engineering 8vo,  4  00 

Fowler's  Sew^age  Works  Analyses 12mo,  2  00 

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Ogden's  Sewer  Construction 8vo,  3  00 

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Rideal's  Disinfection  and  the  Preservation  of  Food Svo,  4  00 

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Soper's  Air  and  Ventilation  of  Subways 12mo,  2  50 

Turneaure  and  Russell's  Public  Water-supplies Svo,  5  00 

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Ward  and  Whipple's  Freshw-ater  Biology.      (In  Press.) 

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*  Typhoid  Fever Large  12mo,  3  00 

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Winslow's  Systematic  Relationship  of  the  Coccaceas Large  12mo,  2  50 


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International  Congress  of  Geologists Large  Svo  1   50 

Ferrel's  Pooular  Treatise  on  the  Winds Svo,  4  00 

Fitzgerald's  Boston  Machinist ISmo,  1  00 

Gannett's  Statistical  Abstract  of  the  World 24mo.  75 

Haines's  American  Railway  Management 12mo.  2  50 

Hanausek's  The  Microscopy  of  Technical  Products.      (Winton) Svo,  -5  00 

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Jacobs's  Betterment    Briefs.     A    Collection    of    Published    Papers    on    Or- 
ganized Industrial  Efficiency 8vo,  $3   50 

Metcalfe's  Cost  of  Manutactures,  and  the  Administration  of  Workshops.. 8vo,  5  00 

Putnam's  Nautical  Charts 8vo,  2  00 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute  1824-1894. 

Large  12mo,  3  00 

Rotherham's  Emphasised  New  Testament Large  8vo,  2  00 

Rust's  Ex-Meridian  Altitude,  Azimuth  and  Star-finding  Tables 8vo,  5  00 

Standage's  Decoration  of  Wood,  Glass,  Metal,  etc 12mo,  2  00 

Thome's  Structural  and  Physiological  Botany.      (Bennett) 16mo,  2   25 

Westermaier's  Compendium  of  General  Botany.      (Schneider) ovo,  '^  (yU 

VVinslow's  Elements  of  Applied  Microscopy 12mo,  1  50 


HEBREW   AND    CHALDEE    TEXT-BOOOKS. 

Gesenius's  Hebrew  and  Chaldee  Lexicon  to  the  Old  Testament  Scriptures. 

(Tregelles.) Small  4to,  half  mor,      5  00 

Green's  Elementary  Hebrew  Grammar 12mo,      1   25 


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FEB  2  5  1959 


^JM  2  2   12B1 


JUN  y  2  19ft 


^JorsT 


m3 


rF_ctJ\)N  30*93 


4UHUJ996 


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WAY  1  0  2000'- 


LD  21-50to-8,'57 
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coe^B^ovbv 


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